Re: 2031LP 75161 wiring question

On 8/5/2018 12:29 PM, Mia Magnusson wrote:
>
> I wounder how hard it would be to change the rom to use PB4 instead of
> PB0 for ATN ack (and therefore also move another signal as all pins are
> used)?
Well, in my design, it's trivial, as it is merely:

assign ieee_bus_ack = b[4];

instead of

assign ieee_bus_ack = b[0];

But, the ROM code needs to be altered as well (I know, Mr. Obvious, but 
for the rest of the folks)
>
> PB4 is the pin used for ATN ack on a 1541 and in 1541 mode the pinout
> needs to be the default for all turbo loaders, copy protection stuff
> and similar to work. But I don't know of any copy protection or "turbo
> load" software for 2031LP, so there might not be any incompatibles.
>
> By swapping PB4 and PB0 the same ATN trap circuit could be used both in
> serial and in IEEE-488 mode.
Hmm, not really, as I will be implementing the trap circuit in the CPLD 
for the IEEE side, so I wouldn't care about the IEC ATN trap circuit.
>
>
> For someone ordering a bunch and
> selling a bunch of ready made conversion kits, like Jim seems to be
> planning, this might not be a problem. But for everyone who like me
> would rather just build a one-off thing it would be nice to be able to
> use whatever is more easily obtained or even something that usually
> already exists in an electronics hobby component box.
Well, Digikey has both in stock.  Farnell or other EU sellers don't?
>
> It seems like the 74AC/ACT family can sink/source 24mA, while the
> 75160/75161 can sink/source 48mA.
I'd look at ABT and ABTH, which can source/sink the right amount. But, 
the '245 transceivers, which seems a reasonable fit, are more expensive 
than the 75160/161.  Your point on unpowered loading still applies, no 
doubt.

Jim