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This photo shows the Southern Cross computer hooked up to the 8x8 LED display & to the simple RS232 interface of Fig.2 which has been built up on a small piece of Veroboard. Peripherals for the Southern Cross Z80 computer This month, we present a number of peripherals for the Southern Cross Z80 computer which was featured in the August 1993 issue of SILICON CHIP. We look at ways to connect the Southern Cross to a person­al computer to make it easy to write programs, introduce an 8x8 LED Matrix display board which can produce interesting visual messages & describe an EPROM emulator. By PETER CROWCROFT & CRAIG JONES 62  Silicon Chip While it is desirable to learn how to enter machine code using the hex keypad of the Southern Cross computer, it is much easier to write these programs on a personal computer and then download them for testing. The fast way to write such programs is to use a text editor on a PC and then use a Z80 assembler to produce a file suitable for downloading to the Southern Cross. A public domain Z80 assem­bler, Z8T, is supplied with the Southern Cross kit and produc­es what is called an Intel hex output file. This is an ASCII file with a checksum every 16 data bytes and other information to help ensure that the transmission can be checked by software at the receiving system. +5V +5V 4.7 RTS V+ 1 C1+ DSR PC SERIAL PORT DB25 TXD RXD 16 TXD 2 VCC 4 C2+ 1 13 14 Q2 BC547 4.7k B 6.8k 1 3 47k D1 1N4148 10 2 CTS PC SERIAL PORT DB25 IC1 C1- MAX232 C2- R1IN R1OUT T1OUT V- T1IN GND 6 SOUTHERN CROSS BIT PORT CN4 5 12 11 RTS 4 SOUTHERN CROSS BIT PORT CN4 E 2.2k DOUT RXD 3 4.7 GND B +5V DSR 6 15 SG E D2 1N4148 CTS 5 DIN 1 DIN 1 C SG 7 C Q1 BC547 C VIEWED FROM BELOW 4.7k DOUT E GND Fig.1 at left is the ideal circuit for an RS-232 serial interface as the MAX232 IC is designed for this job. However, most RS-232 applications for an RS-232 interface for the Southern Cross will be satisfied by the transistor circuit of Fig.2 (right). There are basically two ways to connect the Southern Cross to a PC. First, you can connect it to the serial or parallel port of a PC and download the assembled program from the PC into the RAM space (2000H to 3FFFH). Second, you can use an EPROM emula­tor. In this case, the assembled program is moved to the emulated ROM space (2000H to 3FFFH.) The Monitor uses almost 4K of ROM so there is 4K free for you to use for your own programs. Serial downloading Assuming that you have written a program on your PC and have created an Intel hex file using the Z80 assembler, you will then want to download the hex file to the start of RAM (2000H) on the Southern Cross. By the way, making the jump from a raw novice to being able to write such programs will probably take several weeks at least, assuming that you can devote plenty of time to your Southern Cross, once you have it up and running. We certain­ly do not make light of this achievement but we feel sure that most people who purchase the Southern Cross will do it. The serial port on the Southern Cross is on connector CN4. Unfortunately, this cannot be connected directly to the PC serial port, since it operates on 12V while the Southern Cross operates at 5V. An interface board is required and two such inter- face circuits are shown in Figs. 1 & 2 – see above. For reliable serial communications, the guaranteed way is shown in Fig.1, using a MAX232 IC. A much simpler circuit is shown in Fig.2. This should be adequate in most cases but cannot be guaranteed for all situations. It can be assembled onto a small piece of Veroboard. Three wires are required between the PC and the interface board, while four wires extend from the interface to the Southern Cross. To download the file we must do two things: prepare the Southern Cross to receive the file and then get the PC to send the file. On the Southern Cross go to the address you want to put the file and press Function 1. The Southern Cross is now in ‘ready to receive Intel Hex file’ mode. To send the file from the PC you should first make sure that its serial port is not already being used by a mouse or other hardware item. Next you must set up the port with the DOS command: MODE COM1: 4800,N,8,1 This sets the PC’s port to 4800 baud to match that for the Southern Cross which is set to 4800 baud in the Monitor. Then enter the DOS command COPY filename.hex com1: This starts the file transfer. Alternatively, you could use a communications program, if you have one. When the Intel hex file is fed to the Southern Cross, the Monitor checks that it has been received correctly and converts it into machine code in the correct memory locations. If the transfer was successful a ‘C’ is displayed. Press any key to return to the Monitor. The downloaded file should be in RAM at the address (usually 2000H) it was sent to. If an error has occurred an ‘E’ will be displayed. If it did not come down at all, then nothing will be displayed. The baud rate for file transfer may be changed in software as outlined in the user manual supplied with the Southern Cross. 8 x 8 LED display This add-on board allows you make your own moving message displays. One or two display boards may be Parts List for the 8x8 LED Display 1 PC board, 108 x 60mm 1 CMD-58813 8x8 LED display 2 74HC273 octal D flipflops (IC1, IC2) 1 UDN2981 cathode driver (IC3) 1 ULN2803A anode driver (IC4) 1 DPDT slide switch (S1) 1 10µF electrolytic capacitor 2 18-pin IC sockets 2 20-pin IC sockets 1 16-pin box header connector 1 16-pin IDC socket connector 1 500mm length of 16-strand flat cable December 1993  63 1 10 VCC D7 D6 D5 D4 D3 D2 ROW LATCH I/O SELECT D1 D0 83H S1a 1 3 14 5 12 6 11 7 10 8 9 2 15 16 4 13 VCC 20 CLR O8 18 D8 17 D7 O7 9 19 1 16 4 14 D6 ROW O6 15 13 D5 LATCH 12 8 D4 IC1 O5 74HC273 9 7 D3 O4 4 D2 6 O3 3 D1 5 O2 11 82H O1 CLK 82H 2 5 8 7 6 3 2 O1 I1 I4 I5 O4 I7 O5 I3 O8 83H O7                                                               11 IC4 UDN2981A 10  14 ANODE DRIVER I2  15 I8 I6 LD1 CMD-5881F 18 12 D4 D3 D5 O6 D2 13 D6 D1 O3 16 D7 D8 80H O2 81H RESET 17 18 GND VCC GND 20 SOUTHERN CROSS I/O PORT D7 D6 D5 D4 COLUMN LATCH I/O SELECT 81H S1b 80H D3 D2 D1 D0 18 O8 19 16 O7 15 14 D6 O6 13 12 D5 O5 9 8 D4 COLUMN O4 LATCH 6 7 D3 O3 5 4 D2 O2 IC2 74HC273 3 2 D1 O1 11 CLK 17 1 D8 D7 1 I1 4 5 O1 18 15 O4 O5 14 I4 I5 CATHODE 11 DRIVER O8 I7 O7 12 6 13 IC3 I6 06 ULN2803A 3 03 16 I3 2 17 O2 I2 8 7 I8 9 CLR 10 8x8 DOT LED MATRIX Fig.3: the 8x8 LED matrix display is driven from the parallel port of the Southern Cross computer via two Tri-state latch ICs (IC1 & IC2) & two buffer ICs (IC3 & IC4). Switch S1 switches the latches between two sets of port addresses, thus allowing two LED matrix displays to be used together. used and they are connected to connector CN1 of the Southern Cross. Each board is designed so that the display section may be cut away from the circuit section and connected by flat ribbon cable. The circuit of the 8x8 LED Matrix display is shown in Fig.3. It is connected to the parallel I/O port of the Southern Cross via connector CN1. Data lines D1-D8 are used to drive two 74HC273 octal D-flipflops, each used as 8-bit latches (IC1, IC2). The eight outputs of the two latches are buffered by the UDN2981A anode driver (IC4) and ULN2803A cathode driver (IC3), 64  Silicon Chip respectively. These drive the rows and columns of the 8x8 LED matrix display. Latch IC1 is also connected to the system Reset to ensure that the LEDs are not lit when the circuit is first powered up. Slide switch S1 switches the latches between two sets of port addresses. In this way, two LED Matrix displays can be used together, one operating from port addresses 80h and 82h and the other operating from port address­es 81h and 83h. The LED Matrix display is multi­ plexed and relies on per­sistence of vision to produce its complex patterns so that moving messages (for example) can be displayed. In the kaleidoscope program, each LED may seem to be on all the time but it is not. Each LED is turned on for only 15 microseconds every half a millisecond. This is a duty cycle of 3%. Peak current through the LEDs is 70mA but the average current is only 2mA. Constructing the LED display Assembly of the LED display board does not involve many components and should not take long at all. The component layout diagram is shown in Fig.4. First, fit the 11 wire links to the board. Some of these may be hard to spot. Don’t forget the two short links, near the slide switch. Fit the LED display so that its out- LD1 CMD-5881F D7 1 D6 D5 IC3 ULN2803A D4 D2 10uF 1 IC2 74HC273 1 The 8x8 LED display is, as its name suggests, a matrix of 64 LEDs which are driven in multiplex fashion from the parallel port of the Southern Cross computer. Note the slide switch to change the address of the display, so that two can be used in conjunction with each other. line matches the screen printed outline on top of the board. This is most important because if you do it the other way around the display will be upside down and won’t work. Sockets are supplied for the four ICs and these can be soldered in next. This done, fit the 10µF capacitor, the slide switch and the rightangle flat cable connector. You will have to make up the 16 way cable which uses IDCs (insulation displacement connectors. These are squeezed together with a vise to apply even pressure to the connector halves. When you finish each connector, inspect the pins closely to be sure that each pin is connected to the cable strand that it is supposed to go to. It is rather easy when doing hand construction of these cables to find one pin has gone in skewed and is shorting between two adjacent V-pins. Make sure that pin 1 at one end of the cable goes to pin 1 at the other end, and not pin 16. To check that the board is working the Southern Cross monitor has a kaleidoscope built into it. Put the switch in the up position. This will connect the two latches on the board to ports 80H and 82H. Press Function E. (To remind you – press the Reset key, then the Fn key then the ‘E’ key.) A pattern of ran­ d omly generated D1 D0 IC4 UDN2981 IC1 74HC273 1 S1 symmetric images should appear on the display. This will continue until Reset is pressed. Programming the 8x8 Multiplexing the 8x8 can be done in several ways. One of them is to use the subroutine already written in the Monitor. In this subroutine, SKATE, one row of 8 LEDs is scanned at a time. The LEDs to be turned on in that row are given by the bit pattern of the 8 positions. A bit pattern of 10000001 (or 81h) will turn on the outer two LEDs. A pattern of 11111111 (FFh) will turn them all on. To program this, the byte representing the top row is stored in the register pair HL. HL+1 stores the byte for the second row from the top, HL+2 the byte for row 3 etc. We can conveniently use system call 16 to scan the 8x8 display rather than re-invent the wheel and write our own code. An example will show this more clearly. Using a piece of paper, form the letter A of your choice using the 8x8 SOUTHERN CROSS I/O PORT Fig.4: the component layout of the 8x8 LED matrix display. Do not omit the very short links on either side of the slide switch. matrix. We decided on codes 18, 24, 42, 42, 42, 7E, 7E & 42 as follows: 00011000 = 18h 00100100 = 24h 01000010 = 42h 01000010 = 42h 01000010 = 42h 01111110 = 7Eh 01111110 = 7Eh 01000010 = 42h Do you see the capital A outlined by the 1‘s in the code above and how to derive the hex byte representing the 0 & 1 pat­tern? Hand enter these bytes into locations 2000h to 2007h of the Southern Cross. Next, enter the code shown in Table 1 at 2100h, then do Fn 0. You should have the letter “A” displayed on the LED matrix. Table 1 2100 2103 2105 2106 21 00 20 0E 16 F7 C3 00 21 LD HL,2000H LD C,16H RST 30H JP 2100h ;point HL to buffer ;system call SKATE ;call it ;repeat the loop December 1993  65 33pF RESET S1 33pF X1 6MHz 1 330  TO PC STROBE 6 ERROR 7 BUSY 8 D3 5 D2 4 D1 3 D0 2 GND 1  3 2 4 7 30 29 28 27 34 33 1 P14 A K DIPSW 31 IC1 8748 2 1 B C 330 LED2 READY 10k 10 37 A14 36 A13 35 A12 24 A11 23 A10 22 A9 21 A8 11 19 DB7 18 DB6 17 DB5 16 DB4 15 DB3  47k B Q1 BC547 5D 6D 7D 8D 20 VCC 5O 6O 7O 8O 16 A4 15 A3 14 A2 13 A1 12 A0 E C VCC 11 4 10 1 OC TARGET RESET D1 1N4148 C 4D IC2 4O 74HCT573 17 A5 3D 3O 3 18 A6 2D 2O 2 19 A7 1D 1O 5 6 7 8 13 DB1 14 DB2 9 12 DB0 VIEWED FROM BELOW 3 4 32 39 WR P26 P25 P24 P23 P22 P21 P20 ALE DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 5 P15 T1 SS EPROM EMULATOR 38 XTAL2 P27 XTAL1 RESET EA P13 P12 P11 P10 P17 P16 TB 26 VDD 6 INT 27 1 26 2 23 21 24 25 3 4 5 6 7 8 9 10 WE A14 A13 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 28 20 CE IC3 62256 VCC 14 D7 D6 D5 D4 D3 D2 D1 D0 18 D7 17 D6 16 D5 15 D4 14 D3 13 D2 12 D1 11 D0 A14 17 A12 16 A13 15 A8 14 A9 13 A11 12 A10 11 A0 18 A1 17 A2 16 A3 15 A4 14 A5 13 A6 12 A7 11 D4 D3 D2 D1 20 VCC O4 O3 O2 O1 14 15 16 17 18 7 10 20 E1 E2 1 19 B1 B2 B3 B4 B5 B6 B7 A7 A0 VCC 20 10 E 19 10 A1 A2 A3 A4 IC6 A6 74HCT245 A5 DIR 1 19 D7 D6 D5 D4 D3 D2 D1 D0 A0 A1 A2 A3 A7 A6 A5 A4 VCC 3 A14 4 A12 5 A13 6 A8 7 A9 8 A11 9 A10 2 VCC 9 A7 8 B6 A6 7 B5 A5 6 IC5 A4 B4 74HCT245 5 B3 A3 4 A2 B2 3 B1 A1 2 A0 B0 E 1 DIR B7 D5 IC4 O5 74HCT541 13 D6 O6 9 11 O8 D8 12 8 O7 D7 6 5 4 3 2 D5 D4 D3 D2 D1 D0 28 VCC A5 A4 A3 A2 A1 A0 47k NETWORK D6 4 3 1 2 14 5 VCC A14 A13 A12 A11 A10 A9 A8 A7 A6 5 A5 6 A4 7 A3 8 A2 9 A1 10 A0 VCC 4 A6 28-PIN 3 D7 EPROM A7 SOCKET 25 22 OE A8 24 20 A9 CE 21 A10 23 A11 2 A12 26 A13 27 A14 19 18 17 16 15 13 12 11 A12 10k A14 LED1 DATA A11 A13 66  Silicon Chip The EPROM emulator can be used with the Southern Cross or any other 8-bit computer for that matter. It can emulate 8K, 16K or 32K EPROMs. EPROM emulator ▲ This replaces the EPROM in a computer system with RAM. It has a 28-way cable and 28-pin header plug which takes the place of the EPROM in the target computer. In our case, the target computer is the Southern Cross but it could be any computer system which uses an 8K, 16K or 32K EPROM. The RAM imitates or emulates the EPROM. The target system reads the RAM and thinks it is reading an EPROM. Essentially, it is an independent block of RAM which can be access­ ed from two sides: (1) from the target Fig.5 (left): the EPROM emulator uses an 8748 microcontroller (IC1). This takes data from the host computer a nibble (four bits) at a time & stores it as 8-bit data in a 62256 static RAM (IC3). The target computer then “sees” the RAM as a normal EPROM. X1 2x33pF 1 10k 1 1 IC4 74HCT245 1 10k 1 IC2 74HCT573 This example demonstrates how using the subroutines in the Monitor simplifies code development and reduces time. Just four lines of code have put the contents of the 8-word buffer on the display. Add some bit shift instructions, delays and a bigger message buffer and you can move a message across the screen. Or you can develop a maze game. Examples of each of these types of programs, a maze game and a scrolling message program, have been supplied on the floppy disc which accompanies the 8x8 kit. Now let us look at the last peripheral to be described this month, the EPROM Emulator. 1uF TO PC 1 IC3 8748 IC6 74HCT541 0.1 1 DIPSW 47k Q1 330  S1 OUTPUT TO EPROM IC5 74HCT245 IC3 62256 330  0.1 4x47k D1 LED2 LED1 Fig.6: the component layout for the EPROM emulator. Note that all the ICs are mounted in sockets & must be oriented exactly as shown. The device is connected to the Southern Cross computer via a 28-way flat cable fitted with 28-pin DIP headers. system which can read from it; and (2) from the host PC which can write to it. Hardware and software make sure that simultaneous access from both sides is not possible. The advantage of this system is that program development time can be a matter of seconds rather than tens of minutes or even hours under the old blow-and-erase cycle. The RAM can be written to by the external computer, so the target system imme­diately sees a ‘new’ EPROM. In addition, the emulator gives the capability to download and test other programs in its unused RAM. The emulator described here is an ‘intelligent’ design with an 8748 (or 8749) microcontroller and, as already noted, it can emulate 8K, 16K or 32K EPROMs. A floppy disc with a public domain Z80 assembler is provided as well as a Monitor for the Southern Cross and program examples. The principle of operation is that the program to be tested on the Southern Cross is prepared and assembled in your PC. It is then downloaded to the emulator. While it is being down­ loaded, the Southern Cross system is held in RESET state. When the trans­ fer is successfully completed, a message appears on the PC screen, the Southern Cross system is released from the RESET state and then it is in control. The circuit diagram of the emulator is shown in the diagram of Fig.5. Only four of the eight available data lines from the parallel port are used to transfer data from the PC to the emula­ tor. This results in a saving of two ICs and the elimination of a DB25 port connector on the emulator PC board. The speed cost is about a 10% reduction in data transfer rate compared to that possible if all eight lines were used with DOS commands to do the transfer. This was judged to be an acceptable trade-off in this instance. December 1993  67 Table 2 IDC Pin Name Male Sub-D Pin # Cable Strand # 1 Ground 18-25 1 2 Data line 0 2 3 3 Data line 1 3 5 4 Data line 2 4 7 5 Data line 3 5 9 6 Strobe 1 10 7 Error 15 8 8 Busy 11 9 & 10 Not Connected 6 4 & 2 resp. Prices & availability Since the first article on the Southern Cross in August 1993, the prices for the kits have needed to be adjusted to compensate for currency movements. The prices are as follows: Southern Cross Computer ..................................................................$194 Dallas 1213B SmartSocket ...................................................................$63 Dallas 1216B SmartSocket ...................................................................$84 8x8 LED Display ....................................................................................$73 EPROM Emulator ................................................................................$129 Technical manual of IC data sheets ......................................................$12 The kits containing all the components may be ordered in Austra­lia from Alpine Technology, PO Box 934, Mt Waverley, Vic 3148. Phone or fax (03) 751 1989. You may pay by Bankcard, Mastercard, cheque or money order. Buyers outside Australia should contact DIY Electronics in Hong Kong. Phone/fax (852) 725 0610. The emulator board, emulator software and the software which you are already using in your PC must combine together to operate the EPROM emulator. Power for the emulator comes from the Southern Cross via the 28-pin socket. The 2-way DIP switch selects the size of EPROM to be emulated. The simple RS-232 interface of Fig.2 can be built up on a small piece of Veroboard as shown here. 68  Silicon Chip To emulate the Southern Cross (8K EPROM), both DIP switches will be in the OFF position. The 8748 microcontroller receives the program from the PC a nibble (4 data bits) at a time. It assembles them into bytes (8 data bits) and generates the address and all the timing signals to write the byte into the 62256 static RAM. It also controls the target (ie, the Southern Cross) system via the RESET line, reads the DIP switches, and communicates back to the PC. IC2 is a 74HCT573 Tri-state octal D-type latch which is controlled by the 8748 to switch data from the four input data lines into the addresses of the static RAM (IC3). IC4, IC5 and IC6 are also Tri-state chips which are controlled by the target computer (via the 8748) in accessing data stored in the RAM when the circuit is emulating EPROM. Construction All the components are mounted Parts List for the EPROM Emulator 1 PC board, 114 x 58mm 1 6MHz crystal 1 2-way DIP switch 1 miniature momentary contact switch (S1) 1 200mm-long 28-strand ribbon cable 1 150mm-long 10-strand ribbon cable 2 28-pin DIP headers 1 10-pin IDC connector 1 10-pin box header connector 1 25-pin male sub-D connector 1 25-pin sub-D case 1 40-pin IC socket 1 28-pin IC socket 4 20-pin IC sockets Semiconductors 1 8748 microcontroller (IC1) 1 74HCT573 octal Tri-state D flipflop (IC2) 2 74HCT245 octal Tri-state transceivers (IC5, IC6) 1 74HCT541 octal Tri-state buffer (IC4) 1 62256 static RAM (IC3) 1 BC547 NPN transistor (Q1) 1 1N4148 signal diode (D1) 1 3mm yellow LED (LED 1) 1 3mm green LED (LED2) Capacitors 1 1µF electrolytic 1 0.1µF monolithic 2 33pF ceramic Resistors 1 47kΩ SIL resistor network 1 47kΩ ¼W 1 10kΩ ¼W 1 330Ω ¼W on a double-sided PC board which is screen printed on top to show the layout – see Fig.6. Sockets are used for all the ICs and these can be placed and soldered after all the small components are inserted. Make sure that the transistor, the two LEDs, the diode and the electrolytic capacitor are inserted with correct polarity. A single wire connects the “TO TARGET RESET” pads of the emula­tor to RESET on the target system. Two cables with IDC connectors need to be made up. One cable Continued on page 88 formed per second. Input impedance is 1 Gohms and inputs are protected against over voltages to 200V. There is also a 4-bit isolated output port provided. The LLAD 140 is a 2/3-length card and comes supplied complete with user manual and utility disc. Interfacing is via a DB-15 connector located on the end of the board. For more information, contact Boston Technology Pty Ltd, PO Box 1750, North Sydney, NSW 2059. Phone (02) 955 4765. Australasian satellite TV book Written by Mark Long and Jeffrey Keating, "The World of Satellite TV" gives a comprehensive description of the technology involved in the delivery of satellite TV. It also explains why some installations need big dishes and gives with actual footprints and transponder loadings for satellites in our region. This second edition of "The World of Satellite TV" has been accepted by many as the best satellite book available. It can be purchased from Dick Smith Electronics, Jaycar Electronics or Peter C. Lacey for $29.90 plus $5 pack and postage. The Australian distributor is Peter C. Lacey Sermodule is $299.00. Both modules are rugged circuits with the well-proven Hitachi Mosfets. Get into them while they last. They're available at A-One Elec troncis Pty Ltd, 432-434 Kent Street, Sydney NSW 2000. Phone (02) 267 4819. Low cost 15-bit 4-channel A/D card Boston Technology Pty Ltd has announced the Australian release of the Low cost PC board prototypes vices Pty Ltd, 80 Dandenong Road, Frankston, Vic 3199. Phone (03) 783 2388. LLAD 140 15-bit 4-channel A/D card for PC/XT/AT/386/486 and compatible computers. The LLAD 140 analog interface has four differential analog input channels, each with 0.25mV resolution over an input range of ±5 volts, with excellent stability and noise immunity. Standard linearity is 0.005%. Reproducibility is ±1 count or better. Readings are accurate to within .025% of full scale at normal operating temperatures, and 7.5 conversions are per- Southern Cross Z80 Computer – ctd from p.68 connects the 10-pin IDC socket with the 25-pin Centronics sub-D male connector using 10-strand flat cable. The other cable connects the 28-pin EPROM socket on the target system to the 28-pin EPROM socket on the emulator board. Two identical 28-pin DIP plug connectors have to be con­nected to either end of the 28-strand flat ribbon cable. You need to decide on the cable length which should ideally be no more than 200mm long. The method of making these cables is described above. The parallel port cable has eight connections as listed in Table 2. Make the 10-pin IDC socket connector first. To do this, match cable strand 1 (usually hatched red colour) to the triangle pin 1 moulded in the IDC socket. Press the socket together, then 88  Silicon Chip lay out the cable and the 25-pin male sub-D connector in front of you. Find pin 1 of the IDC connector and solder the other end of the wire to pin 18 of the sub-D connector. Work through pins 2-8 of the 10-pin IDC connector and solder in all eight connections to the sub-D connector as outlined in Table 2 above. Remember that pin 2 of the IDC header is strand three of the ribbon cable, pin 3 is strand five, pin 4 is strand seven, etc. Finally, fit the sub-D cover onto the 25-pin connector to relieve the strain on the solder connections. Does it work? Connect the EPROM emulator to the Southern Cross computer and to your PC and power both systems up. A new PC board manufacturing service has been set up to meet the demand for small volumes of quality double sided, through hole plated boards. By adopting the latest disposable photo tooling techniques, Don Alan has managed to almost eliminate tooling costs. The resulting prices will challenge bread boarding techniques for prototypes and one off manufacturing. Don claims that prices will range from a quarter of the usual price of other PC board manufacturers. All PC boards are 1.6mm fibreglass, double sided, through hole plated, 35µm copper (1 oz), solder resist and component overlayed. Non rectangular and internal profiles and cut outs Type ‘em scmv1_2.hex’ on the PC keyboard. The Data LED should light up on the emulator for about second, then the Ready LED should turn on, the buzzer should sound and ‘2000’ should appear in the Address displays on the Southern Cross (you may have to press the Reset button). If this is OK, enter ‘em 3digit.hex’. Go to Address 1800 and press Function 0. A 3-digit count should be displayed on the right three displays. It should be possible to increase or decrease the readout with the “+” and “-” keys respectively. All the procedures and software for the emulator are sup­plied on a floppy disc which comes with the kit. The designers suggest that the emulator software be used in conjunction with a program such as Norton Commander for most efficient creation of code for SC the Southern Cross.