On 9/9/05, Dwight K. Elvey <dwight.elvey at amd.com> wrote:
As I recall, the GPIB chip made by TI ( forget the
number )
had a data sheet that explained the states. Not much
to it as I recall, mostly just handshake stuff and address
recognition.
The common chips are:
TI TMS9914A
NEC ?PD7210
http://sine.ni.com/nips/cds/view/p/lang/en/nid/1267
It seemed like there was some timed stuff that
might not work well in software but for the most part I'd
suspect that Ethan is right, one could do it all in software.
One issue is to identify what GPIB devices you expect to talk to.
Older ones, especially ones that implemented the protocol via ~1MHz
8-bit microprocessor, are unlikely to be able to handle 1MB/sec speeds
that the newer "IEEE 488.2" devices can. If all you want to do is
talk to old devices at a few KB/sec, it really doesn't matter if you
have a hardware or a software implementation. For the newer,
high-speed stuff, I'd expect you'd need an ASIC to pump the bytes
through in a timely fashion.
OTOH, even Commodore had a little fiddly hardware thing to handle
handshaking turn-around. Andre Fachat mentions that in his extensive
pages covering Commodore hardware and his own home-built
mostly-PET-compatible 6502 computer. I do not know about the
Commodore acoustic couple (C810?), but disks and printers tended to
have 6502/6504/etc software implementation of GPIB.
-ethan