GPIB state machine info WTD - test-drb@ccmp.vtda.org

9 Sep 2005

If you can find it, get a ROM dump or listing from one of the floppy drives
like the 2031LP disk drive or the 2040 dual-drive. The 2031 is a
1541-looking GPIB floppy drive for the PET. 

http://www.funet.fi/pub/cbm/firmware/drives/old/2031/index.html

Here are the ROMs. Just run them through a disassembler and see what you
get. I haven't located a memory map yet.

-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
On Behalf Of Ethan Dicks
Sent: Friday, September 09, 2005 2:53 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: GPIB state machine info WTD

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