Manual - Stanford Research Systems
Contents
1. character follows the mnemonic Set only commands are listed without the query only commands show the after the mnemonic and optionally query commands are marked with a Parameters shown in and are not always required Parameters in are required to set a value and are omitted for queries Parameters in are optional in both set and query commands Parameters listed without any surrounding characters are always required Do not send or or as part of the command Multiple parameters are separated by commas Multiple commands may be sent on one command line by separating them with semi colons so long as the input buffer does not overflow Commands are terminated by either CR or LF characters Null commands and whitespace are ignored Execution of command s does not begin until the command terminator is received Token parameters generically shown as Z in the command de scriptions can be specified either as a keyword or integer value Command descriptions list the valid keyword options with each keyword followed by its corresponding integer value For example to set the response termination sequence to CR lt LF the following two commands are equivalent TERM CRLF or TERM 3 For queries that return token values the return format keyword or integer is specified with the TOKN command SIM965 Bessel amp Butterworth Filter fs RS 2 8 Remote Operati2. 2 5 2 Service Request Enable SRE Each bit in the SRE corresponds one to one with a bit in the SB register and acts as a bitwise AND of the SB flags to generate the MSS bit in the SB and the STATUS signal Bit 6 of the SRE is undefined setting it has no effect and reading it always returns 0 This register is set and queried with the SRE command This register is cleared at power on 2 5 3 Standard Event Status ESR The Standard Event Status register consists of 8 event flags These event flags are all sticky bits that are set by the corresponding event and cleared only by reading or with the CLS command Reading a single bit with the ESR i query clears only bit i Weight Bit Flag 1 0 OPC 2 1 INP 4 2 OYE 8 3 DDE 16 4 EXE 32 5 CME 64 6 URO 128 7 PON OPC INP OYE DDE EXE CME URQ PON Operation Complete Set by the OPC command Input Buffer Error Indicates data has been discarded from the Input Buffer Query Error Indicates data in the Output Queue has been lost Device Dependent Error Not implemented in the SIM965 Execution Error Indicates an error in a command that was successfully parsed Out of range parameters are an example The error code can be queried with LEXE Command Error Indicates a parser detected error The error code can be queried with LCME User Request Indicates a front panel button was pressed Power On Indicates tha
3. Framing Error DO PARITY Parity Error 0 CESR CESE Standard Event Status Status Byte Figure 2 1 Status Register Model for the SIM965 There are two categories of registers in the SIM965 status model Event Registers These read only registers record the occurrence of defined events When the event occurs the corresponding bit is set to 1 Upon querying an event register any set bits within it are cleared These are sometimes known as sticky bits since once set a bit can only be cleared by reading its value Event register names end with SR Enable Registers These read write registers define a bitwise mask for their cor responding event register If any bit position is set in an event register while the same bit position is also set in the enable register then the corresponding summary bit message is set Enable register names end with SE 4 SRS SIM965 Bessel amp Butterworth Filter 2 5 Status Model 2 5 1 Status Byte SB The Status Byte is the top level summary of the SIM965 status model When masked by the Service Request Enable register a bit set in the Status Byte causes the STATUS signal to be asserted on the rear panel SIM interface connector Typically STATUS remains asserted low until a STB query is received at which time STATUS is deasserted raised After clear ing the STATUS signal it will only be re asserted in response to a new status ge
4. The remaining pole of the switch is connected to the filter input In this way the output of the overall filter section circuit can be selected to be either of the three filter types or the fourth option to bypass the filter When the filter is bypassed a second switch is used to ground the filter section input This switching arrangement allows each filter section to be switched in or out of the complete cascaded filter to achieve the desired stop band rolloff slope and passband type The output of the final filter stage is routed back to the digital board which contains the output circuitry see page 3 U303 and U304 form a composite amplifier for the output driver This arrangement provides the driving capability of the BUF634 without suffering its large input offset voltage since the output of U303 is servoed to the noninverting input of U304 via the feedback resistor R315 U305 is a photo MOS switch that remains off during power up until the 15V rails reach about 13V By then analog circuitry have settled permitting the output signal to be connected to the output BNCs without large transients Until switch U305 closes the SIM965 output is referenced to ground via R320 100k The parts list for the analog board is separate from the digital amp front panel boards ASRS SIM965 Bessel amp Butterworth Filter 3 2 Parts Lists 3 5 3 2 1 Digital Board 8 Front Panel Reference SRS P N Value Reference SRS P N Value C10
5. j 2 11 Comm Error Status Enable CESR i 2 11 Comm Error Status CONS z 2 13 Console Mode COUP z 2 9 Input coupling F FREQ f 2 9 Filter Frequency L LBTN 2 14 Button LCME 2 14 Command Error LEXE 2 13 Execution Error O OVLD 2 11 Overload P PARI z 2 10 Parity PASS z 2 9 Filter pass band PSTA z 2 11 Pulse STATUS Mode S SLPE i 2 9 Filter slope T TERM z 2 15 Response Termination TOKN z 2 15 Token Mode ASRS SIM965 Bessel amp Butterworth Filter 2 2 Alphabetic List of Commands TYPE z 2 9 Filter type SIM965 Bessel amp Butterworth Filter ASRS 2 6 Remote Operation 2 3 Introduction Remote operation of the SIM965 is through a simple command lan guage documented in this chapter Both set and query forms of most commands are supported allowing the user complete control of the filter from a remote computer either through the SIM900 Mainframe or directly via RS 232 see Section 1 5 2 1 See Table 1 2 for specification of the DB 15 SIM interface connector 2 3 1 Power on configuration 2 3 2 Buffers 2 3 3 Device Clear 2 4 Commands The settings for the remote interface are 9600 baud with no parity and no flow control and local echo disabled CONS OFF Most of the SIM965 instrument settings are stored in non volatile memory and at power on the instrument returns to the state it was last in when power was removed Exceptions a
6. Example Clear Status CLS immediately clears the ESR and CESR registers and the OVLD bit in the Status Byte CLS ESR 1 Example Standard Event Status Reads the Standard Event Status Register bit i Upon executing ESR the returned bit s of the ESR register are cleared ESR 64 ASRS SIM965 Bessel amp Butterworth Filter 2 4 Commands ESE 1 4 Standard Event Status Enable Set query the Standard Event Status Enable Register bit i to j Example ESE 6 1 ESE 64 CESR 1 Comm Error Status Query Comm Error Status Register for bit Upon executing a CESR query the returned bit s of the CESR register are cleared Example CESR 0 CESE i j Comm Error Status Enable Set query Comm Error Status Enable Register for bit i to j Example CESE 0 OVLD Overload Query the current overload condition The SIM965 responds with 1 during a signal overload and 9 at all other times OVLD always returns the realtime value of overload independent of the value of the OVLD bit in the Status Byte Example OVLD 0 PSTA z Pulse STATUS Mode Set query the Pulse STATUS Mode to Z OFF 0 ON 1 When PSTA ON is set any new service request will only pulse the STATUS signal low for a minimum of 1 us The default behavior is to latch STATUS low until a STB query is received At power on PSTA is set to OFF Example PSTA OFF SIM965 Bessel a
7. a Response 2 25 3 335 4 Time ms Figure 1 3 The nominal step response for Butterworth low pass filters of various orders All filters are tuned to fe 1 kHz SRS SIM965 Bessel amp Butterworth Filter 1 2 Nominal transfer functions 10 20L Response dB F 40 60 12 dB octave 24 48 REN 100 Hz TKZ 10 kHz Frequency Figure 1 4 The nominal frequency response for Bessel low pass fil ters of various orders All filters are tuned to fe 1 kHz o 00 o a 7777 Response 0 36 0 4 48 dB octave 0 2 W o 0 5 1 1 5 2 2 5 Time ms Figure 1 5 The nominal step response for Bessel low pass filters of various orders All filters are tuned to f 1kHz SIM965 Bessel amp Butterworth Filter ASRS Operation 1 2 3 High pass filters Order fo f 34B 2 057739 x f 0 7862 x f 4 031243 x f 0 6604 x f 6 0 21409 x f 0 5787 x fe 8 0 16283x f 0 5177 X f Table 1 1 Bessel filter normalization factors To obtain the formulae for a high pass Butterworth filter simply substitute 1 fo f into Equation 1 1 For a high pass Bessel filter one similarly substitutes 1 f fo into Equation 1 2 However the scaling factors from Table 1 1 must be in verted For example a 6 pole high pass Bessel filter with fe 100 Hz can be calculated using fo fc 0 21409 or 467 09 Hz Figu
8. pending activity it drives the STOP signal high pin 8 of U104 effectively halting its own processor clock In this way the SIM965 guarantees no digital clock artifacts can be generated during quiescent operation ASRS SIM965 Bessel amp Butterworth Filter 3 1 Circuit Descriptions 3 3 3 1 3 Front Panel Display The seven segment displays and LED lamps on the front panel are powered by U204 U208 a daisy chain of 5 74HC595 serial input shift registers The currents to the lamps are limited by resistor networks in series with the displays and LEDs The displays and LEDs are all statically driven i e not multiplexed 3 1 4 Input Coupling and Protection A relay switch K301 in parallel with a capacitor C301 allows for DC or AC input coupling The input signal is buffered by U306 Following that the signal passes through a soft limiting clamp cir cuit to ensure that the input to the filter circuitry does not exceed the 10V input range The limiter consists of resistor R306 and a diode transistor arrangement to actively sink the resistors output current when the input signal goes out of the desired input range This clamps the resistors output voltage This is followed by an ad ditional follower U307 to buffer the signal input to the filter circuitry 3 1 5 Input Overload Detection Input overload is detected via dual comparator U302 with a wire or d output arrangement that is level shifted using Q304 and Q305 This
9. signal is input to the controller 3 1 6 Filter Design The filter design consists of four cascaded biquad state variable fil ters using a combination of analog switches to control the analog signal path The state variable design allows for independent con trol of filter gain cutoff frequency and Q factor These are shown on pages 5 8 of the schematics one biquad per page Component refer ences below are for the first biquad on page 5 reference numbers in the 200 s Equivalent corresponding components for the subsequent stages are numbered in the 300 s 400 s and 500 s respectively Each biquad filter section consists of four multiplying DACs in series with multiple feedback paths The first DAC in the series U207A controls the filter section gain The second DAC U207B controls filter Q factor The remaining two DACs U209A amp U209B are configured as integrators using feedback capacitor banks Analog multiplexers U203 U204 U205 and U208 select the appropriate capacitor combi nations to achieve a desired cutoff frequency range The integrator DACs allow for trimming of the cutoff frequency An attractive feature of the state variable filter architecture is that it provides output taps for low pass high pass and band pass filters SIM965 Bessel amp Butterworth Filter fs RS Circuitry 3 1 7 Output Circuitry 3 2 Parts Lists These taps are fed to three of the inputs to a 4 pole analog switch
10. using a modified state variable circuit design the SIM965 provides a variety of programmed filter configurations From the front panel the user can select a But terworth filter for maximum passband gain flatness or a Bessel filter for minimum pulse overshoot and constand time delay in the passband The user can also select either a low pass or high pass filter and change the order of the filter between 299 4h 6 or 8th order corresponding to 12 24 36 or 48 dB octave roll off in the stop band For any filter configuration a single continuous parameter the cut off frequency fe can be set with 3 digit resolution and 1 ac curacy in the range of 1 Hz to 500kHz For Butterworth filters fe corresponds to the frequency at which the filter response is 3 dB For Bessel filters f is determined so that the far stop band attenuation slope asymptotically approaches that of the Butterworth filter Figure 1 1 The SIM965 front and rear panels SRS SIM965 Bessel amp Butterworth Filter 1 2 Nominal transfer functions 1 3 1 2 Nominal transfer functions 1 2 1 Butterworth filters 1 2 2 Bessel filters The SIM965 circuitry is configured to provide a near ideal Butter worth or Bessel filter transfer function for the user For a Butterworth filter the nominal transfer function for an nth order low pass filter is given by OER 1 1 1 7 where for low pass filters n f fo and fo fc the 3 dB
11. 04 U205 U206 U207 U208 3 00787 74HC595 Q303 3 00601 MMBT3904LT1 U302 3 00728 LM393 Q304 3 00580 MMBT3906LT1 U303 3 01221 BUF634P Q305 3 00601 MMBT3904LT1 U304 3 01289 LT1363CS8 Q306 3 00580 MMBT3906LT1 U305 3 01488 AQY221R2S R101 R105 R110 R111 R124 4 01519 47K U306 U307 3 01218 AD825AR R125 X101 X102 X103 X104 X105 5 00299 1U R102 R112 4 01479 1 0K X106 X107 X108 X109 X301 R103 4 01052 210 X302 X303 X304 X305 X306 R104 R113 R114 R123 4 01527 100K X307 X308 X309 X310 R106 4 01431 10 SIM965 Bessel amp Butterworth Filter ASRS 3 6 Circuitry 3 2 2 Analog Board Reference SRS P N Value Reference SRS P N Value C203 C204 C303 C304 C403 5 00371 47P C238 C239 C338 C339 C438 5 00368 27P C404 C503 C504 C439 C538 C539 C205 C208 C305 C308 C405 5 00616 220P C240 C340 C440 C540 5 00313 1P C408 C505 C508 C241 C341 C441 C541 5 00625 1 8 6 0P RED C209 C210 C309 C310 C409 5 00442 001U C242 C243 C244 C245 C342 5 00318 2 2U T35 C410 C509 C510 C343 C344 C345 C442 C443 C211 C212 C311 C312 C411 5 00450 0047U C444 C445 C542 C543 C544 C412 C511 C512 C545 C213 C214 C313 C314 C413 5 00458 022U J113 1 00638 TSW 113 15 G D C414 C513 C514 PC1 7 01636 SIM965 ANALOG C215 C216 C315 C316 C415 5 00570 1U PPS R202R302 4 01208 8 87K C416 C515 C516 R401R405 4 01242 20 0K C217 C218 C317 C318 C417 5 00617 47U 250V R402 4 01204 8 06K C418 C517 C518 R407 4 01280 49 9K C219 C220 C319 C320 C419 5 00618 2 2U 250V R502 4 01230 15 0K C420 C519 C520 R5
12. 07 4 01251 24 9K C221 C222 C321 C322 C421 5 00574 100P PPS RU507 4 01364 374K C422 C521 C522 U201 U202 U301 U302 U401 3 01328 LT1361CS8 C223 C224 C323 C324 C423 5 00573 470P U402 U501 U502 C424 C523 C524 U203 U204 U206 U208 U303 3 01386 DG408DY C225 C226 C325 C326 C425 5 00446 0022U U304 U306 U308 U403 U404 C426 C525 C526 U406 U408 U503 U504 U506 C227 C228 C327 C328 C427 5 00454 01U U508 C428 C527 C528 U205 U305 U405 U505 3 00787 74HC595 C229 C230 C329 C330 C429 5 00462 047U U207 U209 U307 U309 U407 3 01171 AD5415YRU C430 C529 C530 U409 U507 U509 C231 C232 C331 C332 C431 5 00619 22U 100V U210 U310 U410 U510 3 01367 DG419DY C432 C531 C532 U211 U311 U411 U511 3 01369 DG409DY C235 C236 C335 C336 C435 5 00615 4 7U 63V 5 X201 X220 X301 X320 5 00299 1U C436 C535 C536 3 3 Schematic Diagrams X401 X420 X501 X520 Schematic diagrams follow this page ASRS SIM965 Bessel amp Butterworth Filter
13. 1 5 00381 330P R107 4 01511 22K C102 5 00345 4 0 34P R115 R119 4 01503 10K C105 C106 C107 C302 C305 5 00102 4 7U R116 R118 R120 4 01465 270 C108 C109 C110 5 00387 1000P R117 R121 R122 4 01455 100 C201 C202 C203 C204 C205 5 00299 1U R301 R302 R311 R313 R316 4 01117 1 00K C301 5 00542 1 0U R303 R312 4 01059 249 C306 5 00367 22P R304 R310 4 01242 20 0K C307 C308 5 00318 2 2U T35 R305 4 01067 301 D101 D102 3 00901 BAS40 06 R306 4 01184 4 99K D103 3 00945 BAT54S R307 R309 4 01280 49 9K D201 3 00425 RED R308 4 01405 1 00M D202 D203 D204 D205 D206 3 00424 GREEN R314 4 01021 100 D207 D208 D209 D210 D211 R315 4 01104 732 D212 D213 R317 4 01406 0 D301 D308 3 01357 MMBZ5230 R320 4 01309 100K D302 3 00783 MMBZ5226 R325 R326 4 00913 49 9FP D303 3 01430 BAS40 05 RN201 RN202 RN203 4 00407 2 7K 1206 MINI D304 3 00901 BAS40 06 RN204 RN205 RN206 D305 D306 3 00230 1N5240A RN207 RN208 RN209 RN210 4 00442 1 2K 1206 MINI D307 3 00783 MMBZ5226 201 S202 S203 S204 S205 2 00053 B3F 1052 D309 D310 3 01487 MMBZ5242 206 J211 1 00636 FLE 123 01 GDVA U101 3 00742 74HC74 J212 1 00637 FTSH 123 04 LMT U102 3 01405 MC74AC00D J302 1 00618 SSW 113 01 G D U103 3 00903 MAX6348UR44 JP101 1 00302 6 PIN DIF CES U104 3 01379 MC68HC912B32CFU JP102 1 00367 15PIND U105 3 01390 25LC640 SN K301 3 00617 DS1E ML2 DC5V U106 3 00662 74HC14 L101 L102 L103 6 00174 6611 TYPE 43 U108 3 00663 74HC08 PCB 7 01635 SIM965 DIGITAL U201 U202 U203 3 00290 HDSP A101 Q301 Q302 3 00927 MMBT2907ALT1 U2
14. FREQ 12345 FREQ 1 23E 04 TYPE z Example Filter type Set query the filter type to z BUTTER 0 BESSEL 1 TYPE BESSEL TYPE 1 PASS z Example Filter pass band Set query the filter pass band to z LOWPASS 0 HIGHPASS 1 PASS LOWPASS SLPE i Example Filter slope Set query the filter stop band rolloff rate to i 12 24 36 48 dB octave SLPE 24 SLPE 24 COUP z Example Input coupling Set query the SIM965 input coupling to z DC 9 AC 1 COUP 1 COUP AC SIM965 Bessel amp Butterworth Filter fs RS 2 10 Remote Operation 2 4 5 Serial Communication Commands PARI z 2 4 6 Status Commands Example Parity Set query parity to z NONE ODD 1 EVEN 2 MARK 3 SPACE 4 After power on modules default to PARI NONE PARI EVEN The Status commands query and configure registers associated with status reporting of the SIM965 STB 1 Example Status Byte Reads the Status Byte register bit Execution of the STB query without the optinal bit always causes the STATUS signal to be deasserted Note that STB i will not clear STATUS even if bit is the only bit presently causing the STATUS signal See also the PSTA command STB 16 SRE i i Example Service Request Enable Set query the Service Request Enable register bit i to j SRE 0 1 CLS
15. Operation and Service Manual Bessel amp Butterworth Filter SIM965 SRS Stanford Research Systems Revision 1 7 e August 3 2011 Certification Stanford Research Systems certifies that this product met its published specifications at the time of shipment Warranty This Stanford Research Systems product is warranted against defects in materials and workman ship for a period of one 1 year from the date of shipment Service For warranty service or repair this product must be returned to a Stanford Research Systems authorized service facility Contact Stanford Research Systems or an authorized representative before returning this product for repair Information in this document is subject to change without notice Copyright Stanford Research Systems Inc 2005 2011 All rights reserved Stanford Research Systems Inc 1290 D Reamwood Avenue Sunnyvale CA 94089 USA Phone 408 744 9040 e Fax 408 744 9049 www thinkSRS com e e mail info thinkSRS com Printed in U S A Document number 9 01597 903 SRS SIM965 Bessel amp Butterworth Filter Contents General Information Safety and Preparation for Use SYMDOIS Seii is See ee Sake as Das Notatlon uta od de a he Oe win whe oh we oh A EA Speellieahons E ESE EI eee So 1 Operation LI Overview ae AE we E G 1 22 Nominal transfer functions 1 3 Front Panel Operation 8b Go Be T Clock Stopping ecc Sate as ac
16. a al 1 5 SIMlInterface 2 Remote Operation 2 1 Index of Common Commands 2 2 Alphabetic List of Commands 2 3 Introduction nm nn 24 Commands o ra ie ee 2 5 Status Model 2 22 22 on nn 3 Circuitry 3 1 Circuit Descriptions 22220 war 3 2 Parts Lists il e E a toe ROS ET ern Na 3 3 Schematic Diagrams o os 2 ot al ii Contents ASRS SIM965 Bessel amp Butterworth Filter General Information The SIM965 Analog Filter part of Stanford Research Systems Small Instrumentation Modules family is a continuous time pro grammable filter capable of high pass and low pass operation as a Butterworth or Bessel filter Safety and Preparation for Use La WARNING The front panel input front panel output and the rear panel output coaxial BNC connectors in the SIM965 are referenced to the Earth and their outer casings are grounded No dangerous voltages are generated by the module Do not exceed 15 volts to the Earth at the center terminal of any BNC connector Do not install substitute parts or perform unauthorized modifications to this instrument The SIM965 is a single wide module designed to be used inside the SIM900 Mainframe Do not turn on the power until the module is completely inserted into the mainframe and locked in place 111 iv General Information Symbols you may Find on SRS Products Alternating current Caution ris
17. a subsequent LBTN will return 0 Valid codes are Value Definition 0 no button pressed since last LBTN 1 Freq 4 2 Type 3 Freq Y 4 Slope 5 Filter 6 Coupling Example LBTN 1 ASRS SIM965 Bessel amp Butterworth Filter 2 4 Commands TOKN z Example Token Mode Set query the Token Query mode to Z OFF 0 ON 1 If TOKN ON is set then queries to the SIM module that return to kens will return the text keyword otherwise they return the decimal integer value Thus the only possible responses to the TOKN query are ON and 9 On reset TOKN is set to OFF TOKN OFF TERM z Example Response Termination Set query the term sequence to Z NONE 0 CR 1 LF 2 CRLF 3 LFCR 4 The term sequence is appended to all query responses sent by the module and is constructed of ASCII character s 13 car riage return and 10 line feed The token mnemonic gives the sequence of characters At power on TERM is set to CRLF TERM 3 SIM965 Bessel amp Butterworth Filter fs RS 2 16 Remote Operation 2 5 Status Model The SIM965 status registers follow the hierarchical IEEE 488 2 for mat A block diagram of the status register array is given in Figure 2 1 Communication Error Status DCAS Device Clear 7 47 CTSH CTS Halted ee RTSH RTS Halted aga OVR Input Buffer Overrun aga HWOVRN Hardware Input Overrun aga NOISE Noise Error 22 FRAME
18. ar required parameter for set commands illegal for queries var optional parameter for both set and query forms Filter FREQ f 2 9 Filter Frequency TYPE z 2 9 Filtertype PASS z 2 9 Filter pass band SLPE i 2 9 Filter slope COUP z 2 9 Input coupling Serial Communications PARI z 2 10 Parity Status STB 1 2 10 Status Byte SRE 6 j 2 10 Service Request Enable CLS 2 10 Clear Status ESR i 2 10 Standard Event Status ESE 1 1 j 2 11 Standard Event Status Enable CESR i 2 11 Comm Error Status CESE i j 2 11 Comm Error Status Enable OVLD 2 11 Overload PSTA z 2 11 Pulse STATUS Mode Interface RST 2 12 Reset IDN 2 12 Identify OPC 2 12 Operation Complete CONS z 2 13 Console Mode AWAK z 2 13 Awake mode LEXE 2 13 Execution Error LCME 2 14 Command Error LBTN 2 14 Button TOKN z 2 15 Token Mode TERM z 2 15 Response Termination ASRS SIM965 Bessel amp Butterworth Filter 2 1 Index of Common Commands SIM965 Bessel amp Butterworth Filter ASRS 2 4 Remote Operation 2 2 Alphabetic List of Commands CLS 2 10 Clear Status ESE 1 1 j 2 11 Standard Event Status Enable ESR i 2 10 Standard Event Status IDN 2 12 Identify OPC 2 12 Operation Complete RST 2 12 Reset SRE i j 2 10 Service Request Enable STB i 2 10 Status Byte A AWAK z 2 13 Awake mode C CESE i
19. e SIM965 consists of three separate printed circuit boards the digital board the front panel board and the analog board The digital board is directly beneath the left hand cover as viewed from the front of the module Pages 1 3 of the schematics correspond to the digital and front panel boards Pages 4 9 are the analog board Internally in the SIM965 JP102 pin 1 SIGNAL GND and JP102 pin 8 PS_RTN are tied together on the PCB ground plane JP102 pin 9 CHASSIS_GND is tied to the module chassis through the mounting screws of JP102 CHASSIS_GND is connected to the PCB ground plane through a short wire permanently installed in J101 at the factory The SIM965 is controlled by microcontroller U104 The controller is cloced at 5 MHz A critical aspect of the design is the clock stop circuitry implemented by U101 and U102 A simple RC oscillator is enabled or disabled at pin 1 of U102 which is driven by synchronizing flip flop U101B to ensure that no runt clock pulses are produced that would violate U104 s minimum clock periods Four separate clock starting signals are combined by U106 e Power on reset e Overload any e Incoming serial data e Front panel button press The fast start time of the RC oscillator ensures that incoming se rial data will be correctly decoded by the microcontroller s UART even when the clock is started by the serial start bit of the incoming data When the microcontroller has completed all
20. ed on pin 2 for a low going TTL compatible output indicating a status message 1 5 2 1 Direct interface cabling If the user intends to directly wire the SIM965 independent of the SIM900 Mainframe communication is usually possible by directly connecting the appropriate interface lines from the SIM965 DB 15 plug to the RS 232 serial port of a personal computer Connect RXD from the SIM965 directly to RD on the PC TXD directly to TD In other words a null modem style cable is not needed To interface directly to the DB 9 male DTE RS 232 port typically found on contemporary personal computers a cable must be made with a female DB 15 socket to mate with the SIM965 and a female DB 9 socket to mate with the PC s serial port Separate leads from the DB 15 need to go to the power supply making what is sometimes know as a hydra cable The pin connections are given in Table 1 3 DB 15 F to SIM965 Name DB 9 F 10 3 TxD 11 2 RxD 5 Computer Ground to P S 7 gt 15VDC 13 gt 5VDC 14 15VDC 1 189 lt Ground chassis amp P S return Table 1 3 SIM965 Direct Interface Cable Pin Assignments Although the serial interface lines on the DB 15 do not satisfy the minimum voltage levels of the RS 232 standard they are typically compatible with desktop personal computers SIM965 Bessel amp Butterworth Filter fs RS 1 12 Operation 1 5 2 2 Serial settings The initial serial port settings at p
21. equency 1 00 5x10 Hz Resolution 3 digits Accuracy 1 1 Type Butterworth Bessel Rolloff 12 24 36 48 dB octave Output Noise lt 2004 Vrms 1 MHz bandwidth THD 0 01 80 dB at 1 kHz Operating Temperature 0 40 C non condensing Power 5 15 VDC Supply current 5 V 100 mA 15V 300 mA General Characteristics Interface Serial RS 232 through SIM interface Connectors BNC 2 front 1 rear DB 15 male SIM interface Weight 3lbs Dimensions 1 5 W x 3 6 H x 7 0 D ASRS SIM965 Bessel amp Butterworth Filter 1 Operation In This Chapter This chapter gives you the necessary information to get started quickly with the SIM965 Analog Filter 1 1 1 2 1 3 1 4 1 5 OVERVIEW lt a ia A an ate Nominal transfer functions 1 2 1 Butterworth filters 1 2 2 Bessel filters 2 22 22 222 nn nn 128 High pass filters es yoo Dir Front Panel Operation 131 a A eee pit ont eB a 13 2 AVE ve Ss N eet See o io ae 13 90 Eilter 88 fen aes se tel ten eee A WO Slopers 222 Say Covad Sle A yee a of ok 155 Input rasse a a EB Er 1 36 OUP na 33 EIA E Clock Stopping vivir on Eur ds oS aa SIM Interface a is sn ann 1 5 1 SIM interface connector 1 5 2 Direct interfacing 2 2 20 Suse na Tere Operation 1 1 Overview The SIM965 Analog Filter is a continuous time digitally programmable filter with fully analog signal paths By
22. fre quency of the response function Figures 1 2 and 1 3 show the fre quency and step response for Butterworth low pass filters For Bessel filters the nominal transfer function for an nth order low pass filter is given by 1 G f Ll 3 1 2 dar 2 where for low pass filters n f fo and By Py and boy are determined iteratively based on By 2N 1 Biw 1 1 By 2 with Bo 1 B1 1 Py 2N 1 P n 1 Pa with Po 0 P1 n and bon 2N 1 boqy 1 with boy 1 Figures 1 4 and 1 5 show the frequency and step response for Bessel low pass filters The SIM965 uses a frequency normalization for Bessel filters such that the far stop band response asymptotically approaches that of the same order Butterworth filter Table 1 1 gives the scaling factors to obtain the formal fo needed for the Bessel formulae and the actual 3 dB frequency in terms of the SIM965 setting f For example for a 6 pole low pass Bessel filter with f 100 Hz can be calculated using fo 0 21409 x fo or 21 409 Hz SIM965 Bessel amp Butterworth Filter fs RS 1 4 Operation 20L 12 dB octave Response dB F 40 or 48 dB octave 100 Hz 1 kHz 10 kHz Frequency Figure 1 2 The nominal frequency response for Butterworth low pass filters of various orders All filters are tuned to fe 1 kHz e ro zul i 36 F dB octave 0 4 0 2 W 0 0 5 1 15 o
23. g processing of events Section 1 4 Setting AWAK ON forces the clock to stay running and is useful only for diagnostic purposes AWAK ON LEXE Example Execution Error Query the last execution error code A query of LEXE always clears the error code so a subsequent LEXE will return 0 Valid codes are Value Definition 0 No execution error since last LEXE 1 Illegal value 2 Wrong token 3 Invalid bit 16 Invalid parameter 17 Missing parameter 18 No change STB 12 LEXE LEXE 3 0 The error 3 Invalid bit is because STB only allows bit specific queries of 0 7 The second read of LEXE returns 0 SIM965 Bessel amp Butterworth Filter 5 RS 2 14 Remote Operation LCME Command Error Query the last command error code A query of LCME always clears the error code so a subsequent LCME will return 0 Valid codes are Value Definition 0 No execution error since last LCME 1 Ilegal command 2 Undefined command 3 Illegal query 4 Illegal set 5 Missing parameter s 6 Extra parameter s 7 Null parameter s 8 Parameter buffer overflow 9 Bad floating point 10 Bad integer 11 Bad integer token 12 Bad token value 13 Bad hex block 14 Unknown token Example IDN LCME 4 The error 4 Illegal set is due to the missing LBTN Button Query the last button press code A query of LBTN always clears the button code so
24. k of electric shock Frame or chassis terminal Caution refer to accompanying documents Earth ground terminal SRS SIM965 Bessel amp Butterworth Filter General Information Notation A WARNING A CAUTION The following notation will be used throughout this manual A warning means that injury or death is possible if the instructions are not obeyed A caution means that damage to the instrument or other equipment is possible Typesetting conventions used in this manual are e Front panel buttons are set as Button Adjust AY is shorthand for Adjust 4 amp Adjust 1 e Front panel indicators are set as Overload e Remote command names are set as IDN e Literal text other than command names is set as OFF Remote command examples will all be set in monospaced font In these examples data sent by the host computer to the SIM965 are set as straight teletype font while responses received by the host computer from the SIM965 are set as slanted teletype font SIM965 Bessel amp Butterworth Filter fs RS vi General Information Specifications Performance Characteristics Min Typ Max Units Input Impedance 1 MQ Coupling AC or DC Gain 1x AC coupling time const 1 s Range 48 dB oct Butterworth 5 5 V 36 dB oct Butterworth 7 7 all others 10 10 Filter Band low pass or high pass Cutoff fr
25. mp Butterworth Filter fs RS 2 12 Remote Operation 2 4 7 Interface Commands Interface commands provide generic control over the interface be tween the SIM965 and the host computer RST Reset Reset the SIM965 to default configuration The following commands are internally executed upon RST e FREQ 1 00E 3 e TYPE BUTTER e PASS LOWPASS e SLPE 12 e COUP DC e AWAK OFF e TOKN OFF Example RST IDN Identify Read the device identification string The identification string is formatted as Stanford Research Systems SIM965 s n ver where is the 6 digit serial number and is the firmware revision level Example IDN Stanford Research Systems SIM965 s n003075 ver3 0 OPC Operation Complete Operation Complete Sets the OPC flag in the ESR register The query form OPC writes a 1 in the output queue when complete but does not affect the ESR register Example OPC ASRS SIM965 Bessel amp Butterworth Filter 2 4 Commands CONS z Example Console Mode Set query the Console mode to Z OFF 0 ON 1 CONS causes each character received at the Input Buffer to be copied to the Output Queue At power on and Device Clear CONS is set to OFF CONS 0 AWAK z Example Awake mode Set query the SIM965 keep awake mode to z OFF 0 ON 1 Ordinarily the clock oscillator for the SIM965 microcontroller is held in a stopped state and only enabled durin
26. nerating condition Weight Bit Flag 1 0 OVLD 2 1 undef 0 4 2 undef 0 8 3 undef 0 16 4 IDLE 32 5 ESB 64 6 MSS 128 7 CESB OVLD Overload Status Indicates that an overload has occured IDLE Indicates that the Input Buffer is empty and the command parser is idle Can be used to help synchronize SIM965 query responses ESB Event Status Bit Indicates whether one or more of the enabled events in the Standard Event Status Register is true MSS Master Summary Status Indicates whether one or more of the enabled status messages in the Status Byte register is true Note that while STATUS is released by the STB query MSS is only cleared when the underlying enabled bit message s are cleared CESB Communication Error Summary Bit Indicates whether one or more of the enabled flags in the Communication Error Status Register has become true The OVLD bit is a true event status bit and after being set by an overload the 1 value persists until read by the STB query After a STB query the OVLD bit is cleared to 0 and can only be set back to 1 by a new overload event The remaining bits in the Status Byte are not cleared by the STB query These bits are only cleared by reading the underlying event registers or by clearing the corresponding enable registers 1 but see the PSTA command SIM965 Bessel amp Butterworth Filter fs RS 2 18 Remote Operation
27. of a query through the remote interface However the clock will remain active for as long as the overload condition exists This default behavior can be modified with the remote com mand AWAK Setting AWAK ON will prevent the clock from stopping The module returns to AWAK OFF upon power on SIM965 Bessel amp Butterworth Filter fs RS 1 10 Operation 1 5 SIM Interface AM CAUTION 1 5 1 The primary connection to the SIM965 Analog Filter is the rear panel DB 15 SIM interface connector Typically the SIM965 is mated to a SIM900 Mainframe via this connection either through one of the internal Mainframe slots or the remote cable interface It is also possible to operate the SIM965 directly without using the SIM900 Mainframe This section provides details on the interface The SIM965 has no internal protection against reverse polarity missing supply or overvoltage on the power supply pins Misapplication of power may cause circuit damage SRS recommends using the SIM965 together with the SIM900 Mainframe for most applications SIM interface connector The DB 15 SIM interface connector carries all the power and commu nications lines to the instrument The connector signals are specified in Table 1 2 Direction Pin Signal Src gt Dest Description 1 SIGNALGND MF SIM Ground reference for signal 2 STATUS SIM gt MF Status service request GND asserted 5 V idle 3 RTS MF SIM HW hand
28. on 2 4 2 Notation 2 4 3 Examples The following table summarizes the notation used in the command descriptions symbol definition ij Integers f Floating point values Z Literal token Required for queries illegal for set commands var parameter always required var required parameter for set commands illegal for queries var optional parameter for both set and query forms Each command is provided with a simple example illustrating its usage In these examples all data sent by the host computer to the SIM965 are set as straight teletype font while responses received the host computer from the SIM965 are set as slanted teletype font The usage examples vary with respect to set query optional param eters and token formats These examples are not exhaustive but are intended to provide a convenient starting point for user program ming ASRS SIM965 Bessel amp Butterworth Filter 2 4 Commands 2 4 4 Filter Commands FREQ f Example Filter Frequency Set query the filter cutoff frequency in Hz The valid range for f is 1 00 to 5 00e 5 If f is out of range it will be ignored and the frequency will remain unchanged f can be given in either decimal form 1270 or 3 14 or exponential notation 1 27E 3 or 3 14E 0 but in all cases the value will be truncated to 3 digits Digit truncation occurs after range checking so the value 5 001e 5 is out of range and would be rejected
29. ower on are 9600 Baud 8 bits no parity 1 stop bit and no flow control The parity can be changed with the PARI remote command SRS SIM965 Bessel amp Butterworth Filter 2 Remote Operation In This Chapter This chapter describes operating the SIM965 over the serial interface 2 1 2 2 2 3 2 4 2 5 Index of Common Commands 2 2 Alphabetic List of Commands 2 4 Introduction ip ss Ek 2 6 2 3 1 Power on configuration 2 6 2 32 Buffers ia ee en 2 6 2 3 3 DeviceClear 22222222 nenn 2 6 Eommands s s e aae Era wahr ar when 2 6 2 4 1 Command Syntax sans ren ea sale 2 7 2 4 2 Notation 2 2222 nn 2 8 DAO Examples ee ae a a has een OG 2 8 2 44 FiltereCommands 2 9 2 4 5 Serial Communication Commands 2 10 2 4 6 Status Commands 2 10 2 4 7 InterfaceCommands 2 12 Status Model dico sus ne rn 2 16 20 1 Status Byte SB ea ea 2 17 2 5 2 Service Request Enable SRE 2 18 2 5 3 Standard Event Status ESR 2 18 2 5 4 Standard Event Status Enable ESE 2 18 2 5 5 Communication Error Status CESR 2 19 2 5 6 Communication Error Status Enable CESE 2 19 2 2 Remote Operation 2 1 Index of Common Commands symbol definition ij Integers f Floating point values Z Literal token Required for queries illegal for set commands var parameter always required v
30. re noted in the com mand descriptions Reset values of parameters are shown in boldface Incoming data from the host interface is stored in a 32 byte input buffer Characters accumulate in the input buffer until a command terminator either CR or LF is received at which point the mes sage is parsed and executed Query responses from the SIM965 are buffered in a 32 byte output queue If the input buffer overflows then all data in both the input buffer and the output queue are discarded and an error is recorded in the CESR and ESR status registers The SIM965 host interface can be asynchronously reset to its power on configuration by sending an RS 232 style break signal From the SIM900 Mainframe this is accomplished with the SIM900 SRST command if directly interfacing via RS 232 then use a serial break signal After receiving the Device Clear the interface is reset and CONS mode is turned OFF Note that this only resets the communi cation interface the basic function of the SIM965 is left unchanged to reset the instrument see RST This section provides syntax and operational descriptions for remote commands ASRS SIM965 Bessel amp Butterworth Filter 2 4 Commands 2 4 1 Command Syntax tokens The four letter mnemonic shown in CAPS in each command se quence specifies the command The rest of the sequence consists of parameters Commands may take either set or query form depending on whether the
31. res 1 6 and 1 7 show the frequency response for Butterworth and Bessel high pass filters ASRS SIM965 Bessel amp Butterworth Filter 1 2 Nominal transfer functions 1 7 20L Response dB L 100 Hz 1 kHz 10 kHz Frequency Figure 1 6 The nominal frequency response for Butterworth high pass filters of various orders All filters are tuned to fe 1 kHz 24 36 Response dB i 48 dB octave J J p 1 E 100 Hz 1kHz 10 kHz Frequency Figure 1 7 The nominal frequency response for Bessel high pass filters of various orders All filters are tuned to fe 1 kHz SIM965 Bessel amp Butterworth Filter fs RS 1 8 Operation 1 3 Front Panel Operation 1 3 1 1 3 2 1 3 3 1 3 4 1 3 5 1 3 5 1 Frequency Type Filter Slope Input Couple All settings of the SIM965 can be set from the front panel see Fig ure 1 1 The cutoff frequency can be incremented or decremented using the Freq AT buttons Pressing either Freq 1 or Freq Y once will cause the least significant digit in the display to increment or decrement by one If the button is held down the display will begin to change at a steadily increasing rate accelerating to allow large f changes to be made easily Note that the circuitry is not reprogrammed until the button is released The Type button allows the user to toggle between Butterworth or Bessel filter t
32. ser RTS Holdoff Event Not implemented in the SIM965 CTS Holdoff Event Not implemented in the SIM965 Device Clear Indicates the SIM965 received the Device Clear signal an RS 232 break Clears the Input Buffer and Output Queue and resets the command parser 2 5 6 Communication Error Status Enable CESE The CESE acts as a bitwise AND with the CESR register to produce the single bit CESB message in the Status Byte Register SB It can be set and queried with the CESE command This register is cleared at power on SIM965 Bessel amp Butterworth Filter fs RS Remote Operation ASRS SIM965 Bessel amp Butterworth Filter 3 Parts Lists and Schematics This chapter presents a brief description of the SIM965 circuit design A complete parts list and circuit schematics are included In This Chapter 3 1 Circuit Descriptions 3 202 as ws 8a are 3 2 3 1 1 Grounding 23 ren OS Re 3 2 3 1 2 Microcontroller 3 2 3 13 Front Panel Display 266444446 04904 3 3 3 1 4 Input Coupling and Protection 3 3 3 1 5 Input Overload Detection so one es 3 3 31 6 o A ae ee 3 3 3 1 7 Output Circuitry are 3 4 3 2 Parts Lists Sa esa a eae a he et eae hs 3 4 3 2 1 Digital Board amp Front Panel 3 5 3 2 2 Analog Board ico 222 4 420 84 3 6 3 3 Schematic Diagrams 3 6 3 2 Circuitry 3 1 Circuit Descriptions 3 1 1 Grounding 3 1 2 Microcontroller Th
33. shake unused in SIM965 4 CTS SIM gt MF HW handshake unused in SIM965 5 REF_IOMHZ MF SIM 10 MHz reference no connection in SIM965 6 5V MF gt SIM Power supply no connection in SIM965 7 15V MF gt SIM Power supply 8 PS RTN MF gt SIM Power supply return 9 CHASSIS_GND Chassis ground 10 TXD MF SIM Async data start bit 0 5 V 1 GND 11 RXD SIM gt MF Async data start bit 0 5 V 1 GND 12 REF_10MHz MF SIM 10 MHz reference no connection in SIM965 13 5V MF gt SIM Power supply 14 15V MF gt SIM Power supply 15 24V MF SIM Power supply no connection in SIM965 1 5 2 Direct interfacing Table 1 2 SIM Interface Connector Pin Assignments DB 15 The SIM965 is intended for operation in the SIM900 Mainframe but users may wish to directly interface the module to their own systems without the use of additional hardware ASRS SIM965 Bessel amp Butterworth Filter 1 5 SIM Interface 1 11 The mating connector needed is astandard DB 15 receptacle such as Tyco part 747909 2 or equivalent Clean well regulated supply voltages of 5 15 V DC must be provided following the pin out specified in Table 1 2 Ground must be provided on pins 1 and 8 with chassis ground on pin 9 Note that internally the SIM965 ties all three of these terminals pins 1 8 and 9 together to form the internal ground The STATUS signal may be monitor
34. t an off to on transition has occurred 2 5 4 Standard Event Status Enable ESE The ESE acts as a bitwise AND with the ESR register to produce the single bit ESB message in the Status Byte Register SB It can be set and queried with the ESE command ASRS SIM965 Bessel amp Butterworth Filter 2 5 Status Model This register is cleared at power on 2 5 5 Communication Error Status CESR The Communication Error Status register consists of 8 event flags each of which is set by the corresponding event and cleared only by reading or with the CLS command Reading a single bit with the CESR i query clears only bit i Weight Bit Flag 1 0 PARITY 2 1 FRAME 4 2 NOISE 8 3 HWOVRN 16 4 OVR 32 5 RTSH 64 6 CTSH 128 7 DCAS PARITY FRAME NOISE HWOVRN OVR RTSH CTSH DCAS Parity Error Set by serial parity mismatch on incoming data byte Framing Error Set when an incoming serial data byte is missing the STOP bit Noise Error Set when an incoming serial data byte does not present a steady logic level during each asynchronous bit period window Hardware Overrun Set when an incoming serial data byte is lost due to internal processor latency Causes the Input Buffer to be flushed and resets the command parser Input Buffer Overrun Set when the Input Buffer is overrun by incoming data Causes the Input Buffer to be flushed and resets the command par
35. ype The Filter button allows the user to toggle between high pass or low pass filter pass band The Slope button allows the user to cycle through the four available stop band roll off rates 12 24 36 and 48 dB octave Input signals to the SIM965 at the front panel BNC connector in the Input block If the input signal exceeds the specified 10 V range the Ovld indicator will light and remain on as long as the signal exceeds the specified input range The Coupling button allows the user to toggle the input coupling of the SIM965 between AC and DC coupling When AC coupled the input is high pass filtered by a single pole RC filter with a 1 second time constant ASRS SIM965 Bessel amp Butterworth Filter 1 4 Clock Stopping 1 3 6 Output 1 4 Clock Stopping The filtered signal is available from the SIM965 at the front panel BNC connector in the Output block A second output connector is available on the rear panel as well Each output is separately connected the filter circuitry through an internal 50 Q resistor The microprocessor clock of the SIM965 stops if the module is idle freezing the digital circuitry The following actions wake up the clock 1 A power on 2 A press of a front panel button 3 Activity send or receive at the remote interface 4 An overload The clock runs for as long as is necessary to complete a filter setting adjustment or to communicate the output
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