16-bit Acesses on ISA bus

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Hello!

I have card which generate 16-bit ISA bus timing. I like to know if ISA
bus in 16 bit  generates address bus sequentially 0x0000, 0x0001,
0x0002... or it generates only even/odd addresses.

Thank you and best Regards,
Amir


Re: 16-bit Acesses on ISA bus

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Addresses are byte addresses so for a single 16 bit transaction you need
to use a even (A0=0) address.

unaligned I/O access should be possible (16 bit transfer from odd
addresses) but why do 2 8 bit transfers...

Peter Wallace

Re: 16-bit Acesses on ISA bus
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It's been long long time since my last ISA design. From what I rememebr, 16
bit transfers on ISA bus are always word aligned: i.e. A0 is always 0. This
goes for both memory and I/O. If you can find IBM's "AT technical
reference", you can see the original schematics of the ISA bus interface. As
I remember, the logic there made it impossible to have a 16 bits I/O on the
odd addresses... (I'm telling you all these things off my head. As I said
before, it's been a long long time since my last ISA design).



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