Hi Paul,

Your message is a bit confusing - if you are talking about 80c52 expansion cards then where does ISA slot come in ?

I think you are planning to build a kind of passive backplane which has tracks for +5, GND, Address Bus, Data Bus etc and then slots in it so that you can plug in the CPU and a mix of digital and analog I/O cards as needed. If that is the case, then there has been a thread in this forum - search for term "PC104" or Google for this.

I do use such PCBs ( not as per PC104 though ) - CPU+RS232+EEPROM in one PCB; Isolated 16 channel Digital Input in one PCB; and so on running upto 6 varieties. But I have found that using a 26 Pin FRC header is far more convenient to connect the requitred PCBs, rather than a backplane with slots - when you have slots and guides then the mechanical alignment and such stuff are a big pain.

Raghu