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Backplane

A project log for Old school IC tester

Old school integrated circuit tester/programmer, 100% open source, fully DIY and connectable to anything that provides 11 digital GPIOs

SHAOSSHAOS 05/31/2016 at 04:570 Comments

I decided that interface between ZIF-socket and host machine will be implemented with help of this antique ISA backplane manufactured in 1984 (I bought it for about $20 last month):

I cut out it a little to remove part with pull-up resistors, because it shortened power to the ground somewhere. On the back we can see all signals go through so technically this board could be easily used to implement any custom backplane solution:

For my task I will use part of upside-down ISA-socket where quasi-disks and peripherals (including tester/programmer) will be inserted:

I marked places A,B,C,D,E and F. Also I cut wire that was used as CLK in ISA - now it will be repurposed as individual /CS for every board. Pinout of the socket in this case uses only 42 contacts from socket and most of them repurposed, so it is NOT an ISA bus anymore (I only kept +5V, ground and partially address on their usual locations):

1A0GND42
2A1/CS41
3A2VCC40
4A3X739
5A4X638
6A5X537
7A6X436
8A7X335
9A8A2334
10A9A2233
11A10A2132
12A11D731
13A12D630
14A13D529
15A14D428
16A15D327
17A16D226
18A17D125
19A18D024
20A19/RD23
21A20/WR22

All signals are shared across all sockets except for /CS that individually wired to every slot (8 CS generated by X0,X1,X2 and that's why those 3 bits are not routed into the socket).

You can ask why tester needs quasi disk interface? I think it's cool when device may provide software to control itself right away - so ROM disk C may have a program with component library to run (I can do this program capable to work on many 8080 compatible machine, not only Soviet clones of ZX-Spectrum) and RAM disk A may be used to store test results...

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