Table of Contents
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Table of Contents
SBC-2G-512
Rienk's build.
 |  |
My build diary
Board: Dirtypcbs.com protopack. |  |
Component install: A few parts from junk box. |  |
| Logic install |  |
| VLSI chip install with flash memory card |  |
Z80 SIO/0's 10 pcs pack ex aliexpress.com. Mixed batch received. All 6Mhz parts. Overclock required. Date code: 91'11 - 98'36 |  |
Z80 CPU's 10 pcs pack ex aliexpress.com. All same batch. All 20Mhz parts. Datecode: 00'43 |  |
A 27C256 EPROM can be used in place of the original 27C128, they are both pin compatible. The 27C256 used pin 27 (PGM) as an extra address line A14. 27C128 : 16384Kb : 0000h-3fffh 27C256 : 32768Kb : 0000h-7fffh As only 16Kb is mapped into the memory map only half of the 27C256 can be used. Address line A14 needs to be tied high or low. The SBC-2g-512k board already has A14 tied high to VCC. The only adjustment that needs to be made is to ensure the EPROM is programed starting from 4000h instead of 0000h. i.e the top half is used. |  |
The two serial ports are designated TTY-A and TTY-B. On boot up the monitor ROM will issue a message to both serial ports at 115200kbps. Once it receives a space key press from either port it will boot to the main monitor program using that port for future communication. TTY-A has GND and +5V power connections and the board can be powered from a 5V TTL serial USB converter. I found the voltage supply dropped to 4.7v when using this method. TTY-B does not have +5V power. Ensure only one power source is used at a time, either the 2-pin connector or the the serial connector. |  |
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Parts List
| COMPONENT | PART | NOTES |
|---|---|---|
| R1 | 1M | |
| R2 | 1K | |
| R3, R4, R5, R6, R9, R10 | 4K7 | |
| R7, R8 | 10K | |
| D1 | 1N4148 | Recycled |
| SV1 | ||
| JMP2 | ||
| SV5 | ||
| S1, S2 | ||
| IC1 | Z84C4010 SIO/0 | 6Mhz |
| IC2 | Z84C0006 Z80 | |
| IC3 | N/A | |
| IC4 | 27C128 | Being erase by sun ?!? |
| IC5, IC6 | 74HCT32 | HC |
| IC7 | 74HCT00 | HCT |
| IC8 | 74HCT138 | HC |
| IC9 | 74HCT175 | LS |
| IC10, IC11 | 74HCT02 | HC |
| IC12 | AS6C4008 |
Running BASIC
Rienk provides a hex package for NASCOM ROM BASIC Ver 4.7 which can be loaded from the monitor rom by pasting the contents into the terminal program.
The basic.hex package will be loaded into memory from E000h-FFFFh
The start address to initialize the package is stored in the last two bytes i.e FFFEh-FFFFh and can be confirmed by viewing the memory contents using the “D”ump command:
> DFFF0 FFF0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 6A FD ..............j}
So currently the initialization address is FD6Ah. To start the BASIC package use the “R”un command:
I found this would only work if connected to PORT B.
> RFD6A Cold or Warm? Memory top? Z80 BASIC Ver 4.7b Copyright (C) 1978 by Microsoft 57507 Bytes free Ok
asciiart.bas benchmark for Rienk's sbc-2g-512 7.3728Mhz Z80 board running NASCOM ROM BASIC Ver 4.7:
2m43s
10 FOR Y=-12 TO 12
20 FOR X=-39 TO 39
30 CA=X*0.0458
40 CB= Y*0.08333
50 A=CA
60 B=CB
70 FOR I=0 TO 15
80 T=A*A-B*B+CA
90 B=2*A*B+CB
100 A=T
110 IF (A*A+B*B)>4 THEN GOTO 200
120 NEXT I
130 PRINT " ";
140 GOTO 210
200 IF I>9 THEN I=I+7
205 PRINT CHR$(48+I);
210 NEXT X
220 PRINT
230 NEXT Y
Ok
run
000000011111111111111111122222233347E7AB322222111100000000000000000000000000000
000001111111111111111122222222333557BF75433222211111000000000000000000000000000
000111111111111111112222222233445C 643332222111110000000000000000000000000000
011111111111111111222222233444556C 654433332211111100000000000000000000000
11111111111111112222233346 D978 BCF DF9 6556F4221111110000000000000000000000
111111111111122223333334469 D 6322111111000000000000000000000
1111111111222333333334457DB 85332111111100000000000000000000
11111122234B744444455556A 96532211111110000000000000000000
122222233347BAA7AB776679 A32211111110000000000000000000
2222233334567 9A A532221111111000000000000000000
222333346679 9432221111111000000000000000000
234445568 F B5432221111111000000000000000000
864332221111111000000000000000000
234445568 F B5432221111111000000000000000000
222333346679 9432221111111000000000000000000
2222233334567 9A A532221111111000000000000000000
122222233347BAA7AB776679 A32211111110000000000000000000
11111122234B744444455556A 96532211111110000000000000000000
1111111111222333333334457DB 85332111111100000000000000000000
111111111111122223333334469 D 6322111111000000000000000000000
11111111111111112222233346 D978 BCF DF9 6556F4221111110000000000000000000000
011111111111111111222222233444556C 654433332211111100000000000000000000000
000111111111111111112222222233445C 643332222111110000000000000000000000000
000001111111111111111122222222333557BF75433222211111000000000000000000000000000
000000011111111111111111122222233347E7AB322222111100000000000000000000000000000
Running BASIC from EPROM
The sbc-2g-512 is backward compatible with Grant Searle's original 9 chip CP/M computer. The original monitor and BASIC ROM can be installed.
Use the ROM.HEX file from Grant's original file package http://searle.hostei.com/grant/cpm/index.html#ROMFiles
This run's fine from either port A or B.
https://sourceforge.net/projects/srecord/files/srecord-win32
C:\Users\Phillip\Desktop>srec_cat.exe basic.hex -i -offset -0xE000 -output basic.bin -binary