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my CP/M

4 months ago 134
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This is a CP/M 2.2 computer (pre-IBM). It is working.

It is unique in that it uses the the SIM/RIM instructions and SID/SOD/RST6.5 pins for Serial IO. It uses a 5V USB serial adapter for power and communication to your computer (using a serial terminal program).

There two problems with this approach in that the processing delays between Serial IO means that character can be missed if data is sent by a program (its fine if sent by a human), and many CP/M programs overwrite the RST6.5 vector (so they dont run).

Even so, I have used a CP/M modified version of BASIC/5 (by Processor Tech) on my machine. The current design uses two AT29C256 Flash chips for two 32k "Disk Drives". This is barely enough for any serious use.

If your want to build one yourself then message me for the disk hex files. You will need a Flash programmer to program the Flash chips (I will post my Arduino Nano Flash Programmer later).


I have updated the schematic for 62k RAM and four 128k Flash chips, and a UART. I am using RST7.5 for the UART interrupt. Unfortunately I had to hard draw the PCB (the auto-router just could not do it).

I have also updated the Flash Programmer for the Winbond W29C010. This particular chip uses a 128 byte page which suits CP/M.

I will release the designs (my CP/M II) after I have tested them.



my CP/M

my CP/M


ID Name Designator Footprint Quantity
1 100n C5,C6,C2,C1,C4,C10,C8,C9,C7,C3 RAD-0.2 10
2 MCM6206D U6 DIP28-300 1
3 22k R9,R4,R5,R6,R10,R8,R12,R11,R3,R17,R14,R13 AXIAL-0.4 12
4 1N4148 D1 DO-35 1
5 75k R1 AXIAL-0.4 1
6 1u CR1 RAD-0.2 1
7 33p CX2,CX1 RAD-0.2 2
8 10MHz XTAL HC-49US_L11.5-W4.5-P4.88 1
9 1k R2,R18,R19 AXIAL-0.4 3
10 10u CP1 RAD-0.2 1
11 MC74HC273N U7 DIP20 1
13 47k R15 AXIAL-0.4 1
14 100k R16 AXIAL-0.4 1
15 AT29C256 P9-1,P9-2,P10-2,P10-1 HDR-14X1/2.54 4
16 Cntrl J2 HDR-14X1/2.54 1
17 74HC138 U8 DIP16 1
18 CD74HC373E U5 DIP20 1
19 Intr J1 HDR-8X1/2.54 1
20 8085 P1-1,P1-2 HDR-20X1/2.54 2
21 Bus J3-1,J3-2 HDR-20X1/2.54 2
22 USB-SERIAL P1 HDR-6X1/2.54 1
23 MC74HC02AN U2 DIP14 1
24 MC74HC32AN U4 DIP14 1
25 MC74HC04N U3 DIP14 1




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