[sdiy] Keyboard scanner IC

[Andre Majorel]

On 2009-01-26 13:28 -0500, Nathan M. Reeves wrote:

> yes i think the only chip that is bad is the 6500/11 MCU
> the floppy drive loads samples and the os fine, so the 1772
> seems to be fine....
> not sure what the 6522 does, i guess it also has to do with the
> floppy  drive, which is ok...

The 6522 is a complex chip. It has two 16-bit timers, some 20 I/O
pins and quite a few functions. Some of those I/O pins could be
assigned to the rows and columns of the keyboard.

You could say the 6522 is at least as likely to die as the 6511.
It's closer to the outside world and as such more likely to get
zapped by ESD. It also gets hotter (than a regular 6502, anyway).

Besides Roy's stash, Western Design Center still make the 6522.
The 6502.org folks have an account at WDC. I got some 65xx and
65xxx chips through them a few years ago.

I have no idea where you could find a 6511. I don't even have a
data sheet for it.

I don't see an EPROM in the parts list. Is the 6511 OTP or even
mask-programmed ? If so, pray that it's the 6522...

On a 6502, the SYNC pin will go high when an opcode is fetched,
which should happen at least once every 7 cycles. If the 6511 has
a SYNC pin, you could check that. If the clock is good but SYNC
stays low, it probably means that the chip is dead or stuck on an
invalid instruction.

-- 
André Majorel <URL:http://www.teaser.fr/~amajorel/>