System and method for assigning unique addresses to agents on a
Contents
1. ol 901 6 009 479 Sheet 3 of 6 Dec 28 1999 U S Patent OAUG 4SIG T a vc a 4S L eAuq 4S st o lt a ye vog BuuoyuoJA F3 yun eAug istq fewer siueuoduuo2 uejs g 1 duloo Q ZOE yun tu ls s U S Patent FIGURE 4 Dec 28 1999 Sheet 4 of 6 6 009 479 SMB Master Determine New Address 404 Issue GET BITWISE UID Command 406 Receive UID From Agent 408 Issue SET ADDRESS Command 410 U S Patent Dec 28 1999 Sheet 5 of 6 6 009 479 SMB Slave Response to FIGURE 5 Receive New GET BITWISE UID Command 502 Transmit UID Bit in Byte Transfer 504 Detect Transmission Errors 506 Transmission Error 508 Terminate Transmission Resume Responsiveness to Class Address 514 Count Transmitted Bytes 510 U S Patent Dec 28 1999 Sheet 6 of 6 6 009 479 SMB Slave Response to SET ADDRESS Command Receive New SET ADDRESS Command 602 Compare Local UID to Transmited UID 604 UIDs Match 606 Receive New Unique Address 608 Configure to New Unique Address 610 FIGURE 6 6 009 479 1 SYSTEM AND METHOD FOR ASSIGNING UNIOUE ADDRESSES TO AGENTS ONA SYSTEM MANAGEMENT BUS This application is a continuation in part of copending patent application Ser No 08 389 849 filed on Feb 17 1995 and entitled System And Method For As2. an executable program code for looping a plurality of iterations and setting unique addresses for the plu 3 An apparatus according to claim 1 further comprising a plurality of slave devices coupled to the communica 65 tions medium individual slave devices of the plurality of slave device including a slave controller and a rality of slave devices in the single class 8 An apparatus according to claim 1 further comprising a plurality of N slave devices in a single class coupled to the communications medium individual slave devices 6 009 479 13 of the plurality of slave devices including a slave controller and a hardware identifier designating a fixed slave device identification wherein the program code executable by the master controller further includes an executable program code for looping a N iterations and setting unique addresses for the N slave devices in the single class 9 An apparatus according to claim 1 further wherein the hardware identifier is an SMB agent identifier 10 A computer program product comprising a computer usable medium having computable readable code embodied therein including the program code executable by the master controller and the program code executable by the slave controller according to claim 1 11 A master device for controlling a plurality of slave devices the master device and the plurality of slave devices being coupled by a communications medium the master device comp
3. a plurality of iterations and setting unique addresses for the plurality of slave devices 13 A master device according to claim 11 wherein the plurality of slave devices include a plurality of slave devices of a single class the master device further comprising an executable program code for looping a plurality of iterations and setting unique addresses for the plurality of slave devices in the single class 14 A master device according to claim 11 wherein the plurality of slave devices include a plurality of N slave devices in a single class the master device further compris ing an executable program code for looping a N iterations and setting unique addresses for the N slave devices in the single class 15 20 25 30 35 40 50 55 60 65 14 15 A computer program product comprising a computer usable medium having computable readable code embodied therein including the program code executable by the master controller according to claim 11 16 Aslave device operable in connection with a computer system including a communications medium for connection to the slave device and a master device connected to the communications medium the slave device comprising a slave controller a hardware identifier coupled to the slave controller designating a fixed slave device identification and a program code executable by the slave controller of the slave device including an executable program code fo
4. a speaker Therefore each thermal monitoring card TMC 184A and 184B performs thermal and voltage monitoring operations on a grouping of disk drives in the computer system For more information on the thermal monitoring cards please see the Dell PowerEdge SP 590 2 System User s Guide Appendix C available from Dell Computer Corporation Austin Tex which is hereby incorporated by reference Please also see the Dell PowerEdge XE 590 2 System Service Manual available from Dell which is hereby incor porated by reference The control panel console 192 monitors the status of the hard drives and includes a plurality of LEDs for indicating the status For example a respective LED may be red to indicate the disk drive is not operational orange to indicate that the hard drive is inactive and green to indicate that the hard drive is currently being accessed It is noted that other types of SMB slaves may be comprised within the system which perform other functions as desired In the illustrative embodiment each SMB slave includes a Phillips PCB83C552 Microprocessor In the illustrative embodiment the SCSI adapter 122 includes firmware which enables the adapter 122 to operate as a system management bus SMB master As shown in FIG 2 in an alternate and equally illustrative embodiment the SMB master is configured as a separate dedicated microcontroller 202 connected to the expansion bus 152 It is noted that various other configurations m
5. byte is transmitted as either all one s Oxff or all zero s 0x00 The SMB agents check for transmission errors during the responsive transmission terminate the responsive transmission upon detection of an error and revert to the class address if a unique address was previously assigned The SMB master receives the hardware identifier UID from the SMB agent that successfully transmits the UID The SMB master determines a unique agent address and assigns the unique agent address to the SMB agent that successfully transmitted the hardware identifier UID using the Set Address command The master issues the Set Address command in combination with the unique agent address and the hardware identifier to all SMB agents Only the SMB agent having a hardware identifier US that matches the hardware identifier included in the Set Address command processes the Set Address command to completion successfully changing the SMB address of the agent In accordance with another aspect of the present invention the SMB slave agents are originally configured to operate at a class address At the beginning of the method the SMB master determines whether any of the SMB slaves reside at the class address If so then the SMB master determines a new unique address and issues a Get Bitwise UID command to the slaves residing at the class address Each of the slaves receives the Get Bitwise UID and responsively transmits a hardware identification UID in a
6. code executable by the slave controller of the slave device further includes an executable program code for reverting to an assign ment of a class address to the slave device when the match condition is nonmatching 18 A system operable in connection with a computer system including a communications medium for connection to the system and a master device connected to the com munications medium the system comprising a slave controller a hardware identifier coupled to the slave controller designating a fixed slave device identification and a program code executable by the slave controller of the slave device including an executable program code for receiving a Get Iden tification command transmitted on the communica tions medium by the master device an executable program code responsive to receipt of the Get Identification command for transmitting the fixed slave device identification via transmission on the communications medium detecting errors in 6 009 479 15 transmission of individual bytes of the fixed slave device identification sampling and comparing the individual transmitted bytes with bytes intended for transmission to detect transmission errors updating a count of the number of transmitted bytes if no transmission error is detected determining whether a last byte of the fixed slave identification bytes has been transmitted terminating transmission upon detecting an error and reverting to a class addre
7. identification UID The SMB agent transmits the hardware identifier UID one bit at a time with each bit transmitted as a single byte The individual bits are formatted into bytes for transmission because SMB slaves or agents normally detect transmission errors due to multiple slaves simultaneously transmitting on byte boundaries Since only a bit of information is transmitted in each transmitted byte slaves effectively detect transmission errors on a bit boundary In an illustrative embodiment the responsive byte is transmitted as either all one s Oxff or all zero s 0x00 The SMB agent transmits the hardware identification UID to the SMB master one bit per byte at a time In the illustrative embodiment the SMB agent transmits 64 bytes to the SMB master By convention the SMB data is little endian so that 64 bytes representing 64 bits are transmitted least significant bit first After transmission of a byte representing a single bit of the 64 bit hardware identification UID in operation 504 the SMB slave detects transmission errors during transmis sion of the byte in operation 506 The SMB slave samples the data bus when the slave transmits data but does not automatically respond if a miscompare occurs The SMB slave makes available the entire byte of actually transmitted data and a program executing on the processor compares the actual transmitted byte to the byte intended for transmission to determine whether a transmiss
8. loop of bitwise byte transmissions One slave successfully transmits the hardware identification UID while the other individual slaves detect transmission errors during transmis sion of the hardware identification UID and terminate transmission upon the error detection The unsuccessful slaves if previously residing at a unique address revert to the class address The SMB master receives the hardware identification UID of the successfully transmitting slave and issues a Set Address command in combination with the hardware identification UID and the new unique address to all slave agents at the class address Only the slave agent with a hardware identification UID matching the UID of the Set Address command processes the Set Address com mand to completion and is assigned the SMB address The master uses the Get Bitwise UID command followed by the Set Address command in a loop to locate identify and assign SMB addresses to agents responding to a predeter mined class address The operating loop is advantageously executed exactly once for each of the slave agents connected to the bus avoiding unnecessary instruction cycles latency and expenditure of energy In accordance with an embodiment of the present invention an apparatus includes a communications medium a master device connected to the communications medium and a slave device connected to the communications medium The master device includes a master controller The slave de
9. nonmatching condition is determined 22 Amethod of configuring a system including a plurality of devices connected to a communications medium the devices including a master device and a slave device the slave device including a hardware identifier designating a fixed slave device identification the method comprising determining a unique address issuing a Get Identification command from the master device via transmission on the communications medium receiving the Get Identification command at the slave device via transmission on the communications medium on receipt of the Get Identification command at the slave device transmitting from the slave device the fixed slave device identification via transmission on the communications medium detecting errors in transmis sion of individual bytes of the fixed slave device identification sampling and comparing the individual transmitted bytes with bytes intended for transmission to detect transmission errors updating a count of the number of transmitted bytes if no transmission error is detected determining whether a last byte of the fixed slave identification bytes has been transmitted termi nating transmission upon detecting an error and revert ing to a class address and ceasing to respond to the unique address if a unique address was previously assigned receiving a slave device identification at the master device via transmission on the communications medium and issuing a S
10. program code includ ing an executable program code responsive to receipt of the Set Address command for comparing the received identifi cation and the fixed slave device identification to determine a match condition of matching or nonmatching and an executable program code for assigning the received address to the slave device when the match condition is matching The described system and method achieves many advan tages It is advantageous that the system and method allows multiple devices to be easily and correctly connected to a single master control device Unique addresses are correctly set for the multiple devices without manual selection of hardwired interconnects dip switches or jumpers The illustrative system and method also avoid tedious and error prone manual setting of switches or manipulation of switches through software control It is advantageous that hardware identification is desig nated on a per agent basis so that a master device can associate context with a hardware UID identified agent rather than an address identified agent As agents are added or removed due to disconnection and reconnection to the bus thereby allowing hot plugging context is reassociated with hardware UID identified agents rather than being discarded and recreated BRIEF DESCRIPTION OF THE DRAWINGS The features of the described embodiments believed to be novel are specifically set forth in the appended claims However embodiments of the i
11. slave The slave agents that do not successfully transmit the identifier detect a transmis sion error in the response terminate transmission of the identifier response as a result of the error detection and revert to the class address if a unique address was previously assigned The master sends the Set Address command accompanied by a unique address and an agent identifier to all agent slaves residing at the class address All slave agents at the class address receive the Set Address command but only the agent with the matching agent identifier processes the Set Address command to completion and changes the bus address to the unique address In accordance with a more specific embodiment of the present invention the bus is a system management bus SMB operating under a special protocol in conjunction with a standard PC protocol The FC protocol supports 6 009 479 3 several commands including a Set Address command and a Get Bitwise UID command that are useful for automatically assigning addresses to SMB agents The SMB master issues a Get Bitwise UID command to evoke a responsive trans mission from SMB agents residing on the SMB at the class address The SMB agents respond to the Get Bitwise UID request by transmitting a hardware identifier UID associ ated with the agent The SMB agent transmits the hardware identifier UID one bit at a time with each bit transmitted as a single byte In an illustrative embodiment the responsive
12. unique addresses to agents on a bus The system and method operate to assign unique addresses to devices connected to a bus such as a serial bus or more specifically for some embodiments a serial system management bus The system and operating method for assigning unique addresses to agents on a bus may be used with various types of serial buses and may be incorporated into any of various types of computer systems As shown the computer system includes a processor 102 such as a central processing unit CPU which is connected through a processor local bus 104 to a host PCI cache bridge 106 The bridge 106 connects through a memory bus 108 to a main memory 110 The host PCI cache bridge 106 also interfaces to a peripheral component interconnect PCI bus 120 In the illustrative embodiment a PCI local bus is used However it is noted that other local buses may be used such as the VESA Video Electronics Standards Association VL bus Various types of devices are connected to the PCI bus 120 In the embodiment shown in FIG 1 a video adapter 170 and video frame buffer 172 are connected to the PCI bus 120 for controlling video functions A SCSI small computer sys tems interface adapter 122 is connected to the PCI bus 120 In the illustrative embodiment the SCSI adapter 122 includes firmware which enables the adapter 122 to operate as an SMB master as discussed hereinafter The SCSI adapter 122 includes a SCSI channel 123 which may have var
13. United States Patent ro Jeffries US006009479A 6 009 479 Dec 28 1999 1 Patent Number 4 Date of Patent 54 SYSTEM AND METHOD FOR ASSIGNING UNIQUE ADDRESSES TO AGENTS ON A SYSTEM MANAGEMENT BUS 75 Inventor Kenneth Layton Jeffries Leander Tex 73 Assignee Dell USA L P Round Rock Tex 21 Appl No 08 866 678 22 Filed May 30 1997 Related U S Application Data 63 Continuation in part of application No 08 389 849 Feb 17 1995 Pat No 5 636 342 51 Inf CL aaa G06F 11 00 GO6F 3 00 52 US Cl ete tests 710 8 710 62 58 Field of Search 395 828 829 395 830 831 832 833 874 882 710 814 62 56 References Cited U S PATENT DOCUMENTS 4 679 192 7 1987 Vanbrabant 4 701 878 10 1987 Giinkel et al 4727475 2 1988 Kiremidjian 4 773 005 9 1988 Sullivan 5 148 389 9 1992 Hughes 5 175 822 12 1992 Dixon et al 5 204 669 4 1993 Dorfe et al 5 317 603 5 1994 Cuenod et al 5 379 437 1 1995 Celi Jr et al 5 404 460 4 1995 Thomsen et al 5 483 518 1 1996 Whetsel 5 499 374 3 1996 Di Giulio et al 5 524 269 6 1996 Hamilton et al 5 708 831 1 1998 SCHON see 395 829 Primary Examiner Ayaz R Sheikh Assistant Examiner David A Wiley Attorney Agent or Firm Skjerven Morrill MacPherson Franklin amp Friel LLP Ken J Koestner 57 ABSTRACT A computer system including a bus master performs a me
14. are free to try their transmissions again at a later time The PC serial bus protocol definition does not specify a particular comparison logic for SMB slaves Therefore components operating in slave mode are generally not configured with this bit comparison logic Agents connected to the I C bus are addressed using a unique seven bit code or address In computer systems 10 15 20 25 30 35 40 45 50 55 60 65 8 which utilize a system management bus the computer system may include two or more SMB slaves as shown in either of FIGS 1 2 or 3 Each SMB slave is specified to have its own SMB I C address A designer hardwires a logical address or the unique address is provided by the user manually operating DIP switches or jumpers or using con figuration software to operate logical switches This speci fication to manually or programmatically set addresses of SMB agents can be both tedious and error prone Therefore the disclosed system and operating method assign unique addresses to SMB agents without user involvement Referring to FIG 4 a flowchart diagram illustrates opera tion of a System Management Bus SMB master automati cally assigning addresses to various system management SMB slaves in a computer system In operation 402 the SMB master first determines if any of the SMB slaves reside at an address referred to as the class address The class address is a default address of all agents of a par
15. ass address if a unique address was previously assigned Each of the slaves receives the Get Bitwise UID and responsively transmits the hardware identification UID associated to the slave in a loop of bitwise byte transmissions One slave successfully transmits the hard ware identification UID while all other individual slaves detect transmission errors during transmission of the hard ware identification UID and terminate transmission upon the error detection The unsuccessful slaves if previously residing at a unique address revert to the class address Referring to FIG 6 a flowchart diagram illustrates the response of an SMB agent to a Set Address command of a SMB master In operation 602 the SMB slave receives the Set Address command The Set Address command is issued by the SMB master in combination with arguments includ ing the unique agent address and the hardware identification UID to all SMB slaves In operation 604 the SMB slave compares the received hardware identification UID trans mitted via the Set Address command to the hardware iden tification UID associated generally by hardcoding with the SMB slave If the received and associated hardware identifications UIDs match as determined by the decision operation 606 the SMB agent receives the new unique address from the SMB master in an operation 608 and the SMB slave configures to the new unique address in opera tion 610 completing the operation of assigning th
16. assigned a dedicated IC address for proper operation of the bus The conventional method for assigning addresses to agents on the bus involves a selection 10 15 20 25 30 45 50 55 60 65 2 of hardwired interconnects dip switches or jumpers by a designer The designer specifies dip switch or jumper con nections and a computer system user either manually sets the dip switches or jumpers Alternatively the computer system user uses configuration software to operate logical switches The manual setting of switches or manipulation of switches through software control is often tedious and error prone What is needed is a system and method for automatically assigning addresses to agents on a serial system manage ment bus in a computer system without user intervention What is also needed is a system and method for automati cally assigning unique addresses to new hot pluggable agents that are subsequently connected to the bus SUMMARY OF THE INVENTION In accordance with one aspect of the present invention a computer system including a bus master performs a method for automatically assigning addresses to agents on a bus Addresses are automatically assigned so that a computer system user does not set physical or logical switches either manually or through software programming The system and method also automatically assign unique addresses to new devices that are inserted on the bus while the bus is operati
17. ay be used as desired Referring now to FIG 3 in one embodiment the computer system includes a system unit 302 and a separate external disk drive storage unit 304 for storing additional disk drives In this embodiment the system management bus 180 con nects between the system unit 302 and the external disk drive unit 304 and one or more monitoring devices com prised in the system unit 302 and the external disk drive unit 304 connected to the system management bus 180 As shown the system unit 302 of the computer system includes a plurality of devices connected to the system management bus 180 including two thermal monitoring cards 184A and 184B a control panel console 192 and an SMB master The computer system unit 302 also includes the various com puter system components shown in FIG 1 although these elements are not shown in FIG 3 for simplicity The external disk drive unit 304 includes a plurality of hard drives 124 6 009 479 7 and one or more monitoring devices connected to the system management bus 180 such as one or more thermal moni toring cards 184A and 184B as shown In the illustrative embodiment the system management bus 180 is implemented using the Phillips I C serial bus More specifically in the illustrative embodiment the system management bus is implemented at the electrical level and the lowest protocol level using the I C serial bus protocol An additional protocol is used on top of the FC bus wh
18. ccording to claim 22 kc e
19. ce identification via transmission on terminating transmission upon detecting an error fur the communications medium detecting errors in ther includes transmission of individual bytes of the fixed slave 35 an executable program code for transmitting the fixed device identification sampling and comparing the slave device identification in a plurality of one byte individual transmitted bytes with bytes intended for transmissions one byte corresponding to one bit of transmission to detect transmission errors updating the multiple bit fixed slave device identification a count of the number of transmitted bytes if no an executable program code for comparing data on the transmission error is detected determining whether a o communications and the most recent of the one byte last byte of the fixed slave identification bytes has transmissions and determining a matching condition been transmitted terminating transmission upon or a nonmatching condition and detecting an error and reverting to a class address an executable program code for terminating transmis and ceasing to respond to the unique address if a sion when the nonmatching condition is determined unique address was previously assigned 4s 6 An apparatus according to claim 1 further comprising an executable program code for receiving the Set a plurality of slave devices coupled to the communica Address command via transmission on the commu tions medium individual slave devices of the plurali
20. cludes a system management bus 180 as shown As discussed in the back ground section the system management bus 180 provides 10 15 20 30 35 40 45 50 55 60 65 6 connectivity between various monitoring devices in a sys tem The various monitoring devices connected to the bus 180 operate without involvement of the host processor 102 and operate independently of the operating system In the embodiment shown in FIG 1 the SMB bus includes a plurality of slaves or agents including two or more thermal monitoring cards TMCs 184A and 184B and one or more control panel consoles 192 Thermal monitoring cards TMCs are depicted for exemplary purposes only In other embodiments other types of SMB agents may be employed that are not used for thermal monitoring The TMCs 184A and 184B each measure the temperature and voltages of crucial components within the system For example in one embodiment the TMCs 184A and 184B are each physically situated near a grouping of one or more hard drives and each TMC 184A and 184B monitors tempera tures and voltage fluctuations of the respective grouping of hard drives the associated fan and power supply and the TMC itself If the temperature and or certain measured voltages of one or more drives are not within predefined tolerances the respective thermal monitoring card sounds an alarm which may include turning on LEDs within the respective control panel console 192 or sounding
21. dependently of an operating system that controls the computer system Therefore the system man agement bus operates in parallel with and independently of other operations that are occurring on other buses within the computer system A system management bus is typically used to connect devices called agents Agents monitor operations of other devices in the system and made data accessible for display to a computer user Examples of devices which can be connected to a system management bus include monitoring cards for monitoring disk drive functions control panel consoles for displaying the status of the disk drives within a system and power supply monitors for monitoring and reporting the status of the power supply in the system and the like Devices connected to a system management bus generally perform control functions so the bus specification does not include high speed data transfer capabilities Therefore a system management bus is typically implemented using a serial bus protocol One popular serial bus protocol is an IC serial bus standard protocol developed by Phillips Corpo ration In one implementation the system management bus is implemented at the electrical level and the lowest protocol level using the I C serial bus protocol An additional pro tocol may then be run on top of the FC bus to facilitate data transfers between the devices Each agent connected to a system management bus based on the FC protocol is
22. e Set Address command pro cesses the Set Address command to completion At comple tion of the Set Address process the SMB address of the slave is modified to the assigned unique address The operations performed by the SMB agents or slaves in response to the Set Address command is discussed further hereinafter in the discussion of FIG 6 One SMB slave always responds to the Set Address command issued in operation 410 so that transmission errors by SMB slaves that do not respond to the Set Address command are ignored In operation 402 if none of the SMB slaves are determined to reside at the class address then each of the SMB slaves has received a unique address different from the beginning class address In this case in operation 416 the SMB master waits a period of seconds and during this time other opera tions are performed on the system management bus After a certain period of time has elapsed for example two or three seconds the SMB master returns to operation 402 and repeats the process Thus the SMB master periodically performs the illustrative method If a new SMB slave is added to the SMB bus then within a short period the SMB master performs the above steps and automatically assigns a new unique address to the SMB slave added Since the SMB master periodically performs 6 009 479 9 the automatic configuration to assign unigue addresses to the SMB slaves a new SMB slave is hot pluggable into the SMB bus A new SMB
23. e commu transmission and terminating transmission upon nications medium detecting an error further includes an executable program code for receiving a slave an executable program code for transmitting the device identification via transmission on the com fixed slave device identification in a plurality of munications medium and 90 one byte transmissions one byte corresponding to an executable program code for issuing a Set Address one bit of the multiple bit fixed slave device command via transmission on the communications identification medium the Set Address command designating the an executable program code for detecting transmis unique address and the received slave device iden sion errors on a byte boundary corresponding to a tification and 25 bit boundary of the multiple bit fixed slave device program code executable by the slave controller of the identification slave device including 5 An apparatus according to claim 4 wherein an executable program code for receiving the Get the executable program code executable by the individual Identification command via transmission on the slave devices and responsive to receipt of the Get communications medium 30 Identification command for transmitting the fixed slave an executable program code responsive to receipt of the device identification via transmission on the commu Get Identification command for transmitting the nications medium detecting errors in transmission and fixed slave devi
24. e unique address If the encoded hardware identification UID of the SMB slave does not match the transmitted hardware identification as determined by the decision operation 606 then the SMB slave response to the Set Address command terminates without setting the agent address In summary the SMB master sends the Set Address command to all SMB agents at a predetermined class address the Set Address command including the hardware identification UID argument and the new unique address argument All SMB agents at the class address receive the Set Address command but only the single SMB agent with a hardware identification UID matching the transmitted identification changes assigned address to the new unique address While the invention has been described with reference to various embodiments it will be understood that these embodiments are illustrative and that the scope of the invention is not limited to them Many variations modifications additions and improvements of the embodi ments described are possible For example those skilled in the art will readily implement the steps necessary to provide the structures and methods disclosed herein and will under stand that the process parameters materials and dimensions are given by way of example only and can be varied to achieve the desired structure as well as modifications which are within the scope of the invention Variations and modi fications of the embodiments disclosed here
25. et Address command from the master device via transmission on the communications medium the Set Address command designating the unique address and the received slave device identification and receiving the Set Address command at the slave device via transmission on the communications medium the Set Address command including a received address and a received identification on receipt of the Set Address command at the slave device comparing the received identification and the fixed slave device identification to determine a match condition of matching or nonmatching and assigning the received address to the slave device when the match condition is matching 23 A method according to claim 22 further comprising reverting to an assignment of a class address to the slave device when the match condition is nonmatching 24 A method according to claim 22 wherein the plurality of devices includes a plurality of slave devices coupled to the communica tions medium individual slave devices of the plurality of slave device including a hardware identifier desig nating a fixed slave device identification 25 A method according to claim 22 wherein the plurality of devices includes a plurality of slave devices coupled to the communications medium indi vidual slave devices of the plurality of slave devices including a hardware identifier designating a fixed slave device identification the fixed slave device iden tification being a mul
26. her transfer data to the slave or direct the slave to transmit information to the master Thus the master may reverse transmission directions in cooperation with the addressed slave and thus may either send data to a slave or receive data from a slave Therefore each FC bus agent is either a master or a slave and also is orthogonally either in transmitter mode or receiver mode The PC serial bus protocol provides for arbitration between multiple masters attempting to simultaneously access the bus Arbitration is performed by each master by examining the data actually transmitted on the bus and comparing the transmitted data to the data that the respective master is attempting to transmit The I7C data line is a dot or serial bus where bits from each byte are transmitted serially on the bus According to the PC specification master transmitter hardware examines each bit actually appearing on the bus and compares it with each bit the master is attempting to transmit on a bit by bit basis A master trans mitter ceases transmission if a mismatch occurs The master transmitter that is not in error i e the remaining master transmitter which has not detected an error is able to continue its transmission Thus arbitration between multiple SMB masters is performed on the fly during transmission No agent except the one or more master transmitters in error knows that there has been any problem and the one or more master transmitters in error
27. ication via transmission on the communications medium detecting errors in transmission and terminating transmission upon detecting an error further includes an executable program code for transmitting the fixed slave device identification in a plurality of one byte transmissions one byte corresponding to one bit of the multiple bit fixed slave device identification an executable program code for detecting transmis Sion errors on a byte boundary corresponding to a bit boundary of the multiple bit fixed slave device identification 21 A system according to claim 20 wherein the executable program code executable by the individual slave devices and responsive to receipt of the Get Identification command for transmitting the fixed slave device identification via transmission on the commu nications medium detecting errors in transmission and terminating transmission upon detecting an error fur ther includes an executable program code for transmitting the fixed slave device identification in a plurality of one byte transmissions one byte corresponding to one bit of the multiple bit fixed slave device identification an executable program code for comparing data on the communications and the most recent of the one byte 10 20 25 30 35 40 45 50 55 60 65 16 transmissions and determining a matching condition or a nonmatching condition and an executable program code for terminating transmis sion when the
28. ich defines various bus commands to facilitate data transfers between the devices The FC bus comprises three lines including a serial data line not shown a clock line not shown and a ground wire not shown Each agent connected to the FC bus includes an open collector or dot or connection to the data line Thus if an agent desires to transmit a logical zero on the data line the agent pulls the line low An agent transmits a logical high value on the line by simply floating the line high i e not driving the line For more information on the Phillips IC serial bus please see the Signetics I C Peripherals for Microcontrollers Handbook published January 1992 which is hereby incorporated by reference in its entirety As mentioned above the SMB bus can include a plurality of devices or agents connected to the bus Each SMB agent is a processor controller microcontroller or the like that can operate either in a master or slave mode and can also operate as either a transmitter or receiver The difference between an SMB master and an SMB slave is that the master initiates transactions on the bus For example the master arbitrates and gains ownership of the bus and then initiates a transfer Therefore the master initiates operations first performs arbitration to gain control of the bus and then performs a transmission which includes addressing a slave For example the master can gain control of the bus address a slave and then may eit
29. in may be made based on the description set forth herein without departing from the scope and spirit of the invention as set forth in the following claims 6 009 479 11 What is claimed is 1 An apparatus comprising a communications medium a master device coupled to the communications medium 12 hardware identifier designating a fixed slave device identification 4 An apparatus according to claim 1 further comprising a plurality of slave devices coupled to the communica the master device including a master controller 3 tions medium individual slave devices of the plurality I WAA of slave devices including a slave controller and a slave device coupled t the communications medium hardware identifier designating a fixed slave device the slave device including a slave controller and a identification wherein hardware identifier designating a fixed slave device the fixed slave device identification is a multiple bit identification ali identification and a program code executable by the master controller the executable program code executable by the indi including vidual slave devices and responsive to receipt of the an executable program code for determining a unique Get Identification command for transmitting the address fixed slave device identification via transmission on an executable program code for issuing a Get Identi ye the communications medium detecting errors in fication command via transmission on th
30. ion error has occurred If an error is not detected according to decision operation 508 then in operation 510 the SMB slave updates a count of the number of transmitted bytes and determines whether the transmitted byte is the last byte of the identification bytes In the illustrative embodiment the last byte is the 64th trans mitted byte If the last byte is transmitted as determined by decision operation 512 the response to the Get Bitwise UID operation completes successfully If the transmitted byte is not the last byte in the transfer of the slave identification bytes the decision operation 512 directs that the SMB slave returns to operation 504 and transmits the next hardware identification UID byte The SMB slave repeats operations 504 506 508 510 and 512 until all hardware identification UID bytes are transmitted 10 15 20 25 30 35 40 45 50 55 60 65 10 If the SMB slave detects an error after the transmission of a byte in operation 504 then directed by the decision operation 508 in operation 514 the SMB slave ceases responding to a unique address if a unique address was previously assigned and operative and reverts to respon siveness to the class address In summary the SMB slave agents respond to a Get Bitwise UID command by checking for transmission errors during the responsive transmission terminating the respon sive transmission upon detection of an error and reverting to the cl
31. ious connected devices In the embodiment shown in FIG 1 the SCSI channel 123 includes four disk drive units 124 It is noted that other devices may be connected to the SCSI channel 123 as desired Various other devices may be connected to the PCI bus 120 such as a network interface card 140 As shown the network interface card 140 inter faces to a local area network LAN 142 Expansion bus bridge logic 150 is also connected to the PCI bus 120 The expansion bus bridge logic 150 interfaces to an expansion bus 152 The expansion bus may be any of varying types including the industry standard architecture ISA bus also referred to as the AT bus the extended industry standard architecture EISA bus or the microchan nel architecture MCA bus Various devices may be con nected to the expansion bus 152 including expansion bus memory 154 and a modem 156 The expansion bus bridge logic 150 also connects to a peripheral expansion bus referred to as an X bus 160 The X bus 160 is used for connecting various peripherals to the computer system As shown an interrupt system 162 a real time clock RTC and timers 164 a direct memory access DMA system 166 and ROM Flash memory 168 are connected to the X bus 160 Other peripherals not shown are connected to the X bus 160 including communications ports diagnostics ports command status registers non volatile static random access memory NVSRAM etc The computer system shown in FIG 1 in
32. medium individual slave devices of the plurality of slave devices including a hardware identifier 10 15 20 25 18 designating a fixed slave device identification the method further comprising looping a plurality of iterations and setting unique addresses for the plurality of slave devices 28 A method according to claim 22 wherein the plurality of devices includes a plurality of slave devices of a single class coupled to the communications medium individual slave devices of the plurality of slave device including a hardware identifier designating a fixed slave device identification the method further comprising looping a plurality of iterations and setting unique addresses for the plurality of slave devices in the single class 29 A method according to claim 22 wherein the plurality of devices includes a plurality of N slave devices in a single class coupled to the communications medium individual slave devices of the plurality of slave device including a hardware identifier designating a fixed slave device identification the method further comprising looping a N iterations and setting unique addresses for the N slave devices in the single class 30 A method according to claim 22 wherein the hardware identifier is an SMB agent identifier 31 A computer program product comprising a computer usable medium having computable readable code embodied therein including a program code for performing a method a
33. ng thereby supporting hot pluggable devices In an illustrative embodiment the bus is a system man agement bus SMB operating according to an FC serial protocol The system management bus SMB includes one or more SMB masters and a plurality of SMB slaves The SMB master and SMB slaves perform predetermined moni toring and control operations in the computer system The SMB master performs a method for assigning unique addresses to each of the SMB slaves automatically and without user intervention The disclosed method and system for automatic assignment of addresses advantageously simplifies improves efficiency and avoids error in assigning addresses to bus agents in comparison to conventional manual and software programming techniques In accordance with an embodiment of the present invention the bus operates in compliance with a protocol that includes a plurality of commands Two useful com mands are a Set Address command and a Get Identifier command A master sends the Get Identifier command to slave agents on the bus at a class address The individual slave agents respond to the Get Identifier command by transmitting an identifier identifying the agent When the master issues a Get Identifier command using the agent class address the slave agents at the class address respond and exactly one slave agent successfully transmits an identifier A transmission error occurs when the data on the bus is different from the data sent by a
34. nt with a hardware identification UID matching the UID of the Set Address command processes the Set Address command to completion and is assigned the address The master uses the Get Bitwise UID command followed by the Set Address command in a loop to locate identify and assign addresses to agents responding to a predetermined class address 31 Claims 6 Drawing Sheets Terminate Transmission Resume Responsiveness to Class Address 514 6 009 479 Sheet 1 of 6 Dec 28 1999 U S Patent josuop Jeued Jo3u02 L Old cet Aowan sng uoisuedx3 esi vst wapo 4 BuuolluolN wari gr8l sng uoisuedx3 084 sng 1ueujeDeuel A E SAR SAUP 3 prey rel cah wayshS use ueiss yc PZY ANOU vaa eaup ped Pet esi 991 7 JU NE E pe PN SX eos Zbl i gew waysks ed ied OSI oeu lul Jeydepy 914 idnu ul OPE yiomq N ZZL isos v9L ZO u Sna lod a 0zL H Jeydepy OL O pIA eDpug Kowa sng amp ioueN euoeo sna Teoo1ndO ndo OLL 904 coL 6 009 479 Sheet 2 of 6 Dec 28 1999 U S Patent use ANOH siawi OLY vY9L G o Ola 08L Wapo JB ONUOD I 9SL coz jore jeued l jonuo2 eS BI ean VIAG prey gol Lj SAUP NH 1 orup a wass Zyl prey l pueg aseyaju Joidepy E ji sng lod oZ eDpug ioueN sna owanw uoeoy sna 12007 ndo ule OLL Tv egoi IOdASOH
35. nvention relating to both structure and method of operation may best be understood by referring to the following description and accompanying drawings FIG 1 is a schematic block diagram illustrating a com puter system including a system management bus that is suitable for implementing an embodiment of the system and method of the present invention FIG 2 is a schematic block diagram illustrating an alternate embodiment of the computer system of FIG 1 and including a dedicated SMB master which is connected to an expansion bus of the computer system FIG 3 is a schematic block diagram illustrating a com puter system including a system management bus a system unit and an external disk drive unit FIG 4 is a flowchart diagram illustrating operation of the SMB master which issues Get Bitwise UID and Set Address commands for assigning unique addresses to SMB agents according to an embodiment of the present invention 6 009 479 5 FIG 5 is a flowchart diagram illustrating the response of an SMB agent to a Get Bitwise UID command FIG 6 is a flowchart diagram illustrating the response of an SMB agent to a Set Address command DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT S Referring to FIG 1 a schematic block diagram illustrates a computer system which incorporates a plurality of buses or other communications media including a system manage ment bus and is suitable for implementing a system and operating method for assigning
36. r receiving a Get Iden tification command transmitted on the communica tions medium by the master device an executable program code responsive to receipt of the Get Identification command for transmitting the fixed slave device identification via transmission on the communications medium detecting errors in transmission of individual bytes of the fixed slave device identification sampling and comparing the individual transmitted bytes with bytes intended for transmission to detect transmission errors updating a count of the number of transmitted bytes if no transmission error is detected determining whether a last byte of the fixed slave identification bytes has been transmitted terminating transmission upon detecting an error and reverting to a class address and ceasing to respond to the unique address if a unique address was previously assigned an executable program code for receiving a Set Address command transmitted on the communications medium the Set Address command including a received address and a received identification an executable program code responsive to receipt of the Set Address command for comparing the received identification and the fixed slave device identifica tion to determine a match condition of matching or nonmatching and an executable program code for assigning the received address to the slave device when the match condition is matching 17 A slave device according to claim 16 wherein the program
37. rising a master controller and a program code executable by the master controller including an executable program code for determining a unique address an executable program code for issuing a Get Identi fication command to the plurality of slave devices via transmission on the communications medium an executable program code for receiving a slave device identification via transmission on the com munications medium the slave device identification being sent by a slave device that successfully trans mits the slave device identification the slave device detecting errors in transmission of individual bytes of a fixed slave device identification sampling and comparing individual transmitted bytes with bytes intended for transmission to detect transmission errors updating a count of the number of transmitted bytes if no transmission error is detected determin ing whether a last byte of the fixed slave identifica tion bytes has been transmitted terminating trans mission upon detecting an error and reverting to a class address and ceasing to respond to the unique address if a unique address was previously assigned and an executable program code for issuing a Set Address command via transmission on the communications medium the Set Address command designating the unique address and the received slave device iden tification 12 A master device according to claim 11 further com prising an executable program code for looping
38. signing Unique Addresses To Agents On A System Management Bus by Kenneth L Jeffries now U S Pat No 5 636 342 and which is incorporated herein by reference in its entirety BACKGROUND OF THE INVENTION 1 Field of the Invention The present invention relates to computer systems which include a bus More particularly the present invention relates to a system and method for automatically assigning unique addresses to agents on a bus in a computer system 2 Description of the Related Art Computer systems generally include multiple devices interconnected by one or more various buses For example a typical computer system architecture includes a CPU connected to main memory through a host or memory bus The host or memory bus is connected to an expansion bus In modem computer architectures the expansion bus is typically a local bus such as a peripheral component inter connect PCI bus The local bus may then be connected to a more traditional expansion bus such as an AT bus or Industry Standard Architecture ISA bus an Extended ISA EISA bus or a microchannel architecture MCA bus A computer system often includes a bus referred to as a system management bus used for monitoring operations within the system without involvement of the host processor and or without requiring host processor operability The system management bus operates in the background and does not use CPU resources Thus the system management bus operates in
39. slave subseguently added to the SMB bus receives a unigue address without user intervention Referring to FIG 5 a flowchart diagram illustrates the operation of an SMB slave responding to a Get Bitwise UID command In operation 502 the SMB slave receives the Get Bitwise UID command In response to a Get Bitwise UID command the SMB slave transmits a hardware identifica tion uniquely associated with the SMB slave device The agent devices connected to the system management bus 180 such as the two thermal monitoring cards 184A and 184B the control panel console 192 and the SMB master include an identification hardware One suitable identification hard ware is a Dallas Semiconductor model DS2401 enhanced Silicon Serial Number identification hardware manufactured by Dallas Semiconductor of Dallas Tex that supplies a 64 bit unique hardware identification for an SMB agent Accordingly each SMB agent or slave has a 64 bit unique identification An advantage of having the hardware identi fication designated on a per agent basis is that a master device can associate context with a hardware UID identi fied agent rather than an address identified agent As agents are added or removed due to disconnection and reconnection to the bus thereby allowing hot plugging context is reas sociated with hardware UID identified agents rather than being discarded and recreated In operation 504 the SMB slave transmits a single bit of the 64 bit hardware
40. ss and ceasing to respond to the unique address if a unique address was previously assigned an executable program code for receiving a Set Address command transmitted on the communications medium the Set Address command including a received address and a received identification an executable program code responsive to receipt of the Set Address command for comparing the received identification and the fixed slave device identifica tion to determine a match condition of matching or nonmatching and an executable program code for assigning the received address to the slave device when the match condition is matching 19 A system according to claim 18 further comprising a plurality of slave devices coupled to the communica tions medium individual slave devices of the plurality of slave devices including a slave controller and a hardware identifier designating a fixed slave device identification 20 A system according to claim 18 further comprising a plurality of slave devices coupled to the communica tions medium individual slave devices of the plurality of slave devices including a slave controller and a hardware identifier designating a fixed slave device identification wherein the fixed slave device identification is a multiple bit identification and the executable program code executable by the indi vidual slave devices and responsive to receipt of the Get Identification command for transmitting the fixed slave device identif
41. thod for automatically assigning addresses to agents on a bus Addresses are automatically assigned so that a com puter system user does not set physical or logical switches either manually or through software programming The system and method also automatically assign unique addresses to new devices that are inserted on the bus while the bus is operating thereby supporting hot pluggable devices Slave agents are originally configured to operate at a class address At the beginning of the method a master determines whether any of the slaves reside at the class address If so then the master determines a new unique address and issues a Get Bitwise UID command to the slaves residing at the class address Each of the slaves receives the Get Bitwise UID and responsively transmits a hardware identification UID in a loop of bitwise byte transmissions One slave successfully transmits the hardware identification UID while the other individual slaves detect transmission errors during transmission of the hardware identification UID and terminate transmission upon the error detection The unsuccessful slaves if previously residing at a unique address revert to the class address The master receives the hardware identification UID of the successfully transmit ting slave and issues a Set Address command in combination with the hardware identification UID and the new unique address to all slave agents at the class address Only the slave age
42. ticular type At initialization all of the SMB slaves are initially config ured to operate at class addresses specified for defined agent classes For example all TMCs are initially configured to respond at a first or TMC class address all control panel consoles are initially configured to respond to a second or control panel class address and the like If one or more of the SMB slaves reside at the class address in operation 402 then in operation 404 the SMB master determines a new unique address for the SMB slaves In operation 406 the SMB master issues a Get Bitwise UID command to SMB slaves that reside at the class address The SMB master issues a Get Bitwise UID command to evoke a responsive transmission from SMB agents residing on the SMB at the class address The operation of the SMB slaves in response to a Get Bitwise UID command is discussed further in the description of FIG 5 hereinafter In operation 408 the SMB master receives a hardware identification UID transmitted by one of the SMB slaves the SMB slave that successfully transmits the UID in response to the Get Bitwise UID command In an operation 410 the SMB master issues a Set Address command to the SMB slaves The SMB master issues the Set Address command in com bination with the unique agent address and the hardware identifier UID to all SMB slaves Only the SMB slave having a hardware identifier UID that matches the hard ware identifier included in th
43. tiple bit identification and the operations of transmitting the fixed slave device identification via transmission on the communications 6 009 479 17 medium detecting errors in transmission and termi nating transmission upon detecting an error further includes transmitting from the slave device the fixed slave device identification in a plurality of one byte transmissions one byte corresponding to one bit of the multiple bit fixed slave device identification detecting transmission errors on a byte boundary cor responding to a bit boundary of the multiple bit fixed slave device identification 26 A method according to claim 22 wherein the operations of transmitting the fixed slave device identification via transmission on the communications medium detecting errors in transmission and termi nating transmission upon detecting an error further include transmitting from the slave device the fixed slave device identification in a plurality of one byte transmissions one byte corresponding to one bit of the multiple bit fixed slave device identification comparing data on the communications and the most recent of the one byte transmissions and determining a matching condition or a nonmatching condition and terminating transmission when the nonmatching con dition is determined 27 A method according to claim 22 wherein the plurality of devices includes a plurality of slave devices coupled to the communications
44. ty nications medium the Set Address command includ of slave devices including a slave controller and a ing a received address and a received identification hardware identifier designating a fixed slave device an executable program code responsive to receipt of the so identification wherein the program code executable by Set Address command for comparing the received identification and the fixed slave device identifica tion to determine a match condition of matching or nonmatching and the master controller further includes an executable program code for looping a plurality of iterations and setting unique addresses for the plu rality of slave devices an executable program code for assigning the received 55 address to the slave device when the match condition is matching 2 An apparatus according to claim 1 wherein the pro gram code executable by the slave controller of the slave device further includes 60 7 n apparatus according to claim 1 further comprising a plurality of slave devices of a single class coupled to the communications medium individual slave devices of the plurality of slave devices including a slave control ler and a hardware identifier designating a fixed slave device identification wherein the program code execut an executable program code for reverting to an assign ment of a class address to the slave device when the match condition is nonmatching able by the master controller further includes
45. vice includes a slave controller and a hardware identifier designating a fixed slave device identification The master controller executes a program code including an executable program code for determining a unique address 10 15 20 25 30 35 40 45 50 55 60 65 4 an executable program code for issuing a Get Identification command via transmission on the communications medium an executable program code for receiving a slave device identification via transmission on the communications medium and an executable program code for issuing a Set Address command via transmission on the communications medium The Set Address command designates the unique address and the received slave device identification The slave controller executes a program code including an executable program code for receiving the Get Identification command via transmission on the communications medium and an executable program code responsive to receipt of the Get Identification command for transmitting the fixed slave device identification via transmission on the communica tions medium detecting errors in transmission and termi nating transmission upon detecting an error The slave controller further executes an executable program code for receiving the Set Address command via transmission on the communications medium The Set Address command includes a received address and a received identification The slave controller further executes a
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