PET 4032 keyboard scanning problem / was Re: Anyone have an

Ethan Dicks ethan.dicks at
Fri Apr 9 16:15:43 CDT 2010

On 4/9/10, Brent Hilpert <hilpert at> wrote:
> Great, I'll have to cross-check part numbers sometime to see if there are
> matches for the ones in the 4032 here.

IIRC, your 4032 might or might not have a 6545 CRTC chip.  That's the
critical difference to determine what ROM set you might have - The 12"
PETs all had CRTCs I'm pretty sure, but I'm a bit fuzzy about the
transition between 9" and 12" models.

The ROMs are all uniquely numbered - just check your parts against the
list on  I would be shocked if yours weren't there or at
least mentioned as exact copies of some older part.

>> ... I've even identified three bad 6540 ROM chips...
> Interesting, I'm not familiar with the 6540, not sure if there would be
> any in this 4032.

There would not be.  The 6540 is an oddball MOS ROM with a lot of
select lines and a non-JEDEC pinout.

You will have 2332s in your machine.  They will have a pinout
compatible with a TI2532.  If you do have a bad ROM, you could track
down a TI2532 to replace it, or make an in-socket pin-swabber to
relocate a couple of pins and burn a bog-standard 2732.  I've done

> I actually use a SWTPC 6800 for this sort of thing on occasion: RS232 serial
> to console computer, 6820 PIA lines to DUT, perhaps some intervening hardware
> between the PIA lines and DUT. Write a little 6800 assembler program on the
> console computer, download it to the 6800 to do DUT control and data capture
> and send the data back to the console computer.

Sure.  I did something like that years ago with a 6821 PIA hanging off
of a self-built VIC-20 cartridge (since the protoboards were $3 at
Radio Shack and the VIC-20 was about the cheapest platform I could lay
hands on at the time - $20 or less at hamfests).  What you pick is
largely influenced by when you pick it.

> It would be nice to build up something a little less cumbersome, however. I
> have yet to get around to setting up here for   programming modern
> microcontrollers. I'll take note of the ATmega8515, I was looking at PICs a
> while ago but just wasn't getting enthused about the instruction set.

I am working on an ATmega8515-based clock board with a local friend of
mine (we punted when the 89C52 was giving us some fits, and the 8515
has a compatible pinout, so there were no hardware changes to the
target).  I have a lot of Arduino (ATmega8/168/328) experience, and
I'm a crack C programmer, so I've had zero problems with the 8515 so
far (I'm using a USBtinyISP to program it, in case anyone is curious -
$20 kit from a couple of places) - but you can make non-USB
programmers from scratch less expensively).

I'm really happy with the 8515 - it's powerful enough for what I'm
doing, plenty of code space, I/O, timers, interrupts, etc.  I also use
Arduinos (ATmega8/168/328), helping me keep in the same mindset and
use the same toolchain and programming device.


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