I have trouble to get 16 bit data transferred on ISA bus

[EEHobby]

Hello, Everyone,

I have some troble to get 16 bit data transferred on ISA bus when I have more than one data acquisition board on the PC104. This data acquisition board is my own board. I have an address deconde to generate a read signal, which will read the a FIFO, this read signal also pull IOCS16 pin low on the bus. It work good with one board, but it will not work when I have two board on the bus. Of course, these two board have differnt address. Can anybody give some suggestion? Thanks.


Eric

 

[FvM]

Sounds like IOCS16 is driving the bus (low or high) at times, when the card isn't selected.

 

[bassa]

Hi,

If you think address decoding mechanism is correct then check the IOW and IOR timing cycles (Standard/Manufacturer timing diagram of ISA bus Read and Write cycle) with Logic Analyzer (If you have this facility).

Herewith I attached some details about "ISA I/O Decode" (read example for two I/O cards problems)

I assumed you already built your card according to the ISA timing diagram and if you can give more details about your card (used signals and address etc) then it will much help to understand the issue

Regards
bassa