IEEE-488 interface and Commodore Pet

From: Ethan Dicks <>
Date: Wed Sep 12 16:46:21 2001

--- Tony Duell <> wrote:
> > That sounds a little like what I have... Mine are National Instruments
> > 180212-01, Rev A PCBs (c. 1984), silk-screened to Assy. No. 180210-0.
> > The main chip is an NEC 7201, the IEEE-488 interface chips are Nat.
> Semi
> I'll bet that's a typo for 7210.

Oops. Sure is.

> > There's a five-position DIP switch labelled "0, 1, 2, 14, 13", which I
> > take to be a GPIB address, a bank of jumpers marked
> I wonder if that might be part of the I/O address. Lines 0,1,2 and 13,14.
> IIRC, the IBM GPIB card did decode address lines other than the normal 10
> used by most I/O devices. The top ones were used to select between
> multiple GPIB cards in the same machine IIRC.

Hmm... good point. I do recall seeing some stuff about how wierd the
addressing normally is (something about the progression for multiple
cards going like 0x03ee, 0x04ee, 0x05ee, then something like 0x3e1...
I don't recall the actual numbers off the top of my head.) I don't
have an ISA spec in front of me - is there an A13 and A14 on an 8-bit

> That last set might be 'Request' and 'Acknowldge' for DMA? In other words
> a DMA channel select.

> > indicating that it could have a Lithium coin cell, a 58167...
> The 58167 is a real time clock IIRC. In which case the Xtal is almost
> certainly a 32.768kHz one. They normally come in a tiny cylindrical can.

The silk-screen shows an oval spot with the leads spaced about .2" apart.
I expect that it was for one of those flush-mount .1" tall Xtal cans.
The small cylindrical ones I've seen on motherboards could be made to
fit with no problem.

> You can probably raid the 58167 off an old XT real time clock card, or
> some older AT motherboards, or the like.

Good point. Did AT motherboards have them? I've mostly seen Dallas
chips with embedded batteries on clone boards.

> The other passives aren't that critical. The values of the capacitors
> connected to the crystal (around 22pF) you can get from the 58167 data
> sheet. Try 10k for any pull-up resistors and 0.1uF ceramic for decoupling
> capacitors. That should be a start.

Good tip.

Now the problem is what kind of software support there is for these. One
thing I might do (eventually) is to cobble up a driver for the GG2 Bus+
for the Amiga *if* DMA is optional. If DMA is required, it's a no-go.


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Received on Wed Sep 12 2001 - 16:46:21 BST

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