I've recently been playing around with my new Clearview Mathias emulator,
getting a feel for it. I decided to actually start working on my first
project with it, and noticed something odd, perhaps a bug (or a blunder on
my part). I am using the Parallel Slave Port (16C74). When I write a byte
to the port (to be read by the external device), the correct bit in TRISE
is set, and then cleared when the byte is read. No problem. However, when I
externally write a byte into the PSP, the correct status bit in TRISE is
*not* set, according to the emulator that is. The bit is actually being
set, because a small snippet of code that mirrors that bit to a digital
output works correctly.

I noticed that the emulator errata in the documentation mentions that the
Mathias does not correctly display I/O latch information? (or something
like that, I'm at home and the docs are at work)

Has anyone else noticed this? Is there a work around? It's not too big of a
deal, as the actual programs work, it just makes it tougher to see what's
actually happening.

Also, for my first project, I plan on having the 16C74 make around 32 bytes
available on the PSP. Any suggestions on the handshaking necessary to make
sure that the external device does not read the PSP before the pic has had
the time to update the PSP with the next byte? I'm planning on using the
interrupt from the PSP to get the pic to make the next byte of data
available. For those interested, the pic will serve as a sort of
"pre-processor", reading conversion data from eight A/D converters, and
then making the data available on the PSP, to be read by a PC104 CPU.
(There will actually be 24 pic / A/D modules in the system)

Chris


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