Southern Cross 2 Hardware Manual. pdf file.
Contents
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3. address the range 0000h to I FFFh is directed to internal Program memory Any other program address is directed externally It is possible to direct all program access externally by disabling internal program memory This is done by connecting the EA pin to ground The 8031 32 series have no internal program memory so all program access must be directed externally The microcontrollers running BASIC are 8052 series chips with the BASIC interpreter stored in internal program memory Program memory can only be read not written to The PSEN signal is used as a read strobe for any external program memory Data memory occupies a separate address space from Program memory The RD and WR signals are used to access external Data memory as needed Only Data memory can be written to and programs can only run from Program memory It is possible to combine all or part of the Program and Data memory into one address space This is done by logically ORing the PSEN and RD signals with the decoded memory range required and using the resultant output as a read strobe Combining Program and Data memory is necessary on the Southern Cross II so that users can download and run programs The Southern Cross provides 16K of RAM memory that is accessible as both Program and Data memory This is the area of memory where user programs are downloaded into and executed from The other 16K of RAM is accessible as Data memory only The EPROM can be 8K 16K or 32
4. port Connection is via the 10 pin header labelled J6 2 Uses an external SC2691 UART chip from Philips Components and is referred to as the HOST port Connection is via the 10 pin header labelled J5 The RS 232 signals are brought out to standard D9 connectors by using 10 way flat ribbon cable One end is terminated with a 10 pin IDC plug and the other end with a crimp style female D9 connector By connecting pin 1 on the 10 pin plug with pin 1 on the D9 connectors the signals will be in the correct positions to allow a straight through connection to a D9 type PC COM port RS 232 Interface J5 J6 Signal J5 J6 pin D9 pin TxD 3 2 RxD 5 3 CTS 6 8 DSR 2 6 GND 9 5 DCD 1 1 Parallel I O Ports A number of parallel I O ports are provided Some are static in operation meaning that any data written to the port is latched The other ports are dynamic in nature These ports do not latch data written to them Output data is only valid while the port is being addressed These ports are referred to as bit ports 8031 I O ports J1 The 8051 family of microcontrollers have four inbuilt 8 bit parallel ports labelled 0 3 Two of these ports PO and P2 are used as address data busses when external program and data memory access is required This is the mode in which the Southern Cross operates Port bits P3 6 and P3 7 are used as RD WR signals and therefore are not available for use as I O lines This leaves 13 I O line
5. the EPROM The Southern Cross II generates this programming voltage using a DC DC converter chip IC12 The Southern Cross II is designed to use a 27256 EPROM for storing BASIC programs These EPROMs require a programming voltage of 12 5 volts Before attempting to save any programs in EPROM the programming voltage must be set to this level This is done by measuring the voltage on test pin and adjusting trimpot VR1 for 12 5 volts This procedure is only required once However it is worth checking this voltage periodically or whenever any problems occur with saving programs to EPROM The Southern Cross II only uses 27256 EPROMs for saving BASIC programs Remove the MVS 31 monitor EPROM and install a 27256 type in its place The MVS 31 monitor can reside on the same 27256 EPROM used to save BASIC programs The monitor would reside in the bottom 8K starting at address 0000h whereas BASIC programs are saved at address locations 8000h upwards which is in the upper 16K of the EPROM The memory decoder GAL IC9 splits the EPROM into two halves with half starting at 0000h and the other half starting at 8000h Remember to set jumper JP2 to the correct EPROM type A number BASIC 52 programming and startup options are also available Refer to the BASIC 52 reference manual for further details BASIC 52 uses port bits P1 3 P1 4 and P1 5 as EPROM programming control lines The function of these lines is P1 3 ALE Disable P1 4 Program p
6. to 1200 2400 4800 9600 or 19200 bps 5 Turn on the power via switch SW3 LED D2 should light 6 Press the space bar to trigger the BASIC 52 automatic baud rate detection A sign on message will appear followed by a READY prompt Commands may now be entered PADS Please read the section on BASIC 52 Programming before attempting to save any programs into EPROM EPROM types The Southern Cross II can use three different EPROM types 8K 2764 16K 27128 and 32K 27256 The EPROM type is selected by setting jumper JP2 to the correct position as marked on the circuit board Note that in order to save BASIC programs in EPROM a 27256 EPROM must be used Southern Cross Memory Map This manual does not aim to provide a detailed explanation of the architecture of the 8051 family of microcontrollers However a short description is necessary so that the memory decoding scheme can be explained and understood The 8051 family of microcontrollers implement the Harvard memory architecture This means that these devices have separate address spaces for Program and Data memory each up to 64K in size Internal circuitry in the microcontroller accesses the correct memory based on the instruction being executed As well as having separate Program and Data spaces these microcontrollers also have internal and external Program and Data memory The 8051 52 series of microcontrollers can have up to 8K of internal program memory Thus any program
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8. DIY Electronics Southern Cross II 8031 Single Board Computer Hardware Manual DIY Electronics HK Ltd PO Box 88458 Sham Shui Po Hong Kong Fax 852 2304 2250 Voice 852 2729 1400 Email sales kitsrus com http www kitsrus com May 2002 Introduction The Southern Cross II single board computer is based around the 8032 52 8 bit microcontroller Adding a power supply and connecting to any PC capable of running an 8051 cross assembler enables the user to implement an 8031 software development system Programming in BASIC is also possible using one of the 8052 BASIC chips currently available If your board is fitted with one of these BASIC chips then switching from one software environment to the other is simply a matter of inserting or removing a link The Southern Cross when used in conjunction with the MVS 31 debugging monitor implements complete 8031 based assembly language software development system The extra resources provided by an 8032 52 over an 8031 extra timer and an additional 128 bytes of internal RAM memory together with an independent external UART allows the user complete access to all the 8031 s internal ports and timers Software debugging tools such as breakpoints watchpoints and single stepping are provided by the MVS 31 monitor program Refer to the MVS 31 User s manual for further details Getting Started Running in 8031 mode Insert the MVS 31 monitor EPROM into socket IC4 and ensure that ju
9. K type The EPROM address space is split with 16K located at 0000h and the other 16K located at 8000h The 16K block at 8000h is used to store BASIC programs when the Southern Cross II is used as a BASIC computer Refer to the BASIC 52 Programming reference manuals for more information All external I O devices such as the SPI and PPI chips are located in external data memory Remember that only data memory can be written to Figure 1 gives an overall picture of the Southern Cross memory map Memory and I O decoding is provided via two programmable logic devices GALs Using GALs for address mapping adds great flexibility to the circuit design as well as significantly reducing chip count Other memory and I O address mapping schemes are possible by re programming the GALs Contact DIY Electronics for further information External External Program Data Memory Memory 0000h EPROM 0000h 5 31 Common program and gt data space 7FFFh 8000h F000h VACANT F400h F800h FCOOK FDOOh FEO0h 8000h BIT PORT 4 FF00h Serial Ports These are implemented as simple 3 wire interfaces using just TxD RxD and GND The modem control lines CTS DSR and DCD are held at the RS 232 ON level and do not provide any hardware handshaking No software handshaking protocol is used either The Southern Cross has two serial ports 1 Uses the internal serial port of the 8032 52 chip and is referred to as the USER
10. ations Bit port 1 Bit port 2 FDOOh Bit port 3 FE00h Bit port 4 FFOOh Although each port is mapped into a 256 byte block it is only one address wide Therefore bit port 1 can be accessed at address etc right through to FCFFh These ports are both input and output ports depending on the instruction used to access them These ports are pin for pin compatible to the CN1 port on the Z80 based Southern Cross computer also available from DIY Electronics It is provided on the Southern Cross II to take advantage of a number of add on boards already available for the Southern Cross computer The bit ports are brought out to a 16 pin header labelled J4 5 irporT3 6 m ID 8 9 4 0 Expansion Interface J3 A maximum of 256 bytes of I O expansion is available via connector J3 This interface allows for further devices to be connected to the microcontroller The interface is mapped in external data memory beginning at address location F800h g 2 2 AL O gt 230 2 a __ _ 25 x GND Signals preceeded by are active low other signals are active high The signal IOEXP is the block decode signal for the expansion interface and should be used in conjunction with address lines AO A7 to provide further address decoding Address lines AO A7 have already been
11. d at frank ozitronics com The following web sites contain 80xx code amp material http www lvr com http Aivewire ee latrobe edu sjm http cera2 com gatox805 htm http Awww atmel com 3 of 3 Revision 1 Sheet Drawn boa pas Ean Ea d Ea a Ea d Es a Ea Ea d or O O 5 G O NM 00 m 00 0 0 oti T co 1 D O t SINGLE BOARD COMPUTER CPU amp MEMORY T NM 00 IC3 74HC573 8031 CONTROL BUS ADDRESS BUS RAM_ OE 3 Po Po el S 9 2 SYS ALE 11 DATA BUS BUF_DIR EPROM PROG LINK IF NO DECOUPLING CAPS ROM_ CE 26 ROM tO DM 25 ROM 14 1 YCC on re xxXZZOn le oe ll ol SS SS OANMELD s s s sss A e a AAAA
12. de mulitplexed on the Southern Cross board ie they are actually address lines This allows devices with separate address and data lines to be connected to the expansion interface directly For those devices with a multiplexed address data bus use signals ADO AD7 and ALE Clock Calendar An optional clock calendar device is available for the Southern Cross a Dallas Semiconductor DS1216C Intelligent Socket Access to this clock calendar is provided in the MVS 31 debugging monitor The DS1216C contains an internal lithium battery This keeps the clock going during power down and also makes the CMOS RAM non volatile ie no loss of data when power to the Southern Cross is removed Battery life is over 10 years No circuit modifications are necessary to use the DS1216C just plug it in between the RAM chip and the IC socket or solder directly to the PCB if purchased with the Southern Cross II kit BASIC 52 Programming As mentioned the Southern Cross board is capable of being programmed in BASIC A number of suppliers such as Intel and Micromint Inc have available an 8052 microcontroller with a BASIC interpreter programmed into the chip s internal EPROM The Southern Cross needs one of these chips installed as in order run the BASIC 52 language BASIC 52 has the ability to store its programs into an external memory device such as EPROM Programming EPROM requires a voltage level of between 12 5 and 25 volts depending
13. mper JP2 is set to the correct EPROM type An 8032 52 microcontroller chip must be used in position IC1 Insert a link on jumper JP1 Move switch SW2 to the OFF position Connect a 9 12 volt DC plug pack via power connector J7 Connect the supplied serial cable to connector 5 port Connect a terminal or PC running terminal emulation software to the D25 connector on the cable Configure the terminal or PC serial port to 8 data bits 1 stop bit and no parity The baud rate should be set to 1200 2400 4800 9600 or 19200 bps 5 Turn on the power via switch SW3 LED D2 should light 6 Press the Carriage Return Enter key to trigger the MVS 31 automatic baud rate detection A sign on banner will appear followed by gt prompt Commands may now be entered Running in BASIC mode This mode requires an 8052 BASIC microcontroller chip in position IC1 A 27256 EPROM is also necessary in position IC4 if BASIC programs are to be saved into EPROM Ensure that jumper JP2 is set to the correct EPROM type Remove the link from jumper 1 1 Move switch SW2 to the OFF position Connect a 9 12 volt DC plug pack via power connector J7 Connect the supplied serial cable to connector J6 port Connect a terminal or PC running terminal emulation software to the D25 connector on the cable Configure the terminal or PC serial port to 8 data bits 1 stop bit and no parity The baud rate should be set
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15. s available for use all of port 1 and bits 0 5 of port 3 Note that port bits P3 0 P3 5 all have secondary functions eg P3 0 and P3 1 are the Rx and Tx lines for the 8031 serial port These 13 I O lines are brought out to a 16 pin header labelled 5 1 4 6 5 gt _ 0130 80 0 Port bits P1 3 P1 4 ans P1 5 also have secondary function They are connected via switch SW2 to memory decoder GAL IC9 and used by the 8052 BASIC chips as EPROM programming control pins These pins are only needed by BASIC 52 when programs are to be saved into EPROM Refer to the section on BASIC 52 Programming for further details 8255 I O Ports J2 Three 8 bit parallel ports are implemented using the 8255 Programmable Peripheral Interface PPI chip This chip is mapped in external data memory at address F400h These 24 I O lines are brought out to a 26 pin header labelled J2 5 Il6 5 _ PROS o BE Bit Ports J4 As mentioned previously these are dynamic not static ports With referrence to sheet 2 of the schematic diagram the 8 I O lines are actually driven by the data bus BADO 7 The ports are formed by decoding a 256 byte memory block and using the resulting output as an active low strobe similar to the chip enable signals for the EPROM and RAM chips These 4 bit ports are mapped in external data memory at the following address loc
16. ulse width P1 5 Enable program voltage These signals are not connected directly to the EPROM or associated programming circuitry Instead they are connected via switch SW2 and the memory decoder GAL IC9 When the GAL detects a low on its pin 5 it uses these port bits to control the output signals ROM_CE SYS_ALE VPP_CONT Moving SW2 to the ON position connects the port bits to the GAL and pulls pin 5 low ready for EPROM programming These port bits can also be used as general purpose I O lines and are brought out on connector J1 These pins MUST be isolated from any external voltage levels This would be the case if any of these pins were inputs being driven from a device connected to J1 Therefore it is advisable before saving programs to EPROM to disconnect any device from To summarize the following steps must be carried out before issuing a BASIC 52 programming command 1 Disconnect any device attached to connector J1 2 Move switch SW2 to the ON position Whilst the MVS 31 monitor program and BASIC programs can be stored on the same 27256 EPROM it is advisable to use two separate EPROMS If you wish to keep them together then make copy of MVS 31 EPROM and use the copy instead The MVS 31 binary file is on the disk supplied with the Southern Cross computer References The hardware amp software for the Southern Cross 2 were developed by Frank Crivelli for DIY Electronics Frank can be contacte
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