Re: Apple II Interrupt card

[et472@FreeNet.Carleton.CA (Michael Black)]

Exegete (millers@noneofyourbusiness.com) writes:
> The GEOS/Berkeley Softworks supplied an "IRQ Manager" card for the Apple 
> IIe that did not have a mouse card. I have two of these cards. They only 
> have two chips on them:
> 
> SN74LS161AN
> 
A 4-bit synchronous binary counter.
This would seem to be the datasheet:
   http://www.ee.washington.edu/stores/DataSheets/74ls/74ls161.pdf
though I did not take the time to look at it.
A simple pinout is here
   http://www.xs4all.nl/~ganswijk/chipdir/pinusr/74161.txt

> and
> 
> SN74LS03N
> 
Quad 2-input nand gate with open collector output.  The fact that
this has an open collector is a big hint that it connects to
the interrupt line.
Again, a likely datasheet is this:
   http://www.ee.washington.edu/stores/DataSheets/74ls/74ls03.pdf

One might guess from context, that the counters are cascaded,
and are fed from a clock signal on the Apple bus, providing
an interrupt, via the 74LS03, to the interrupt line.

   Michael