One more try - Can you ID this S-100 Serial board?
chrise at pobox.com
Thu Oct 1 18:56:36 CDT 2015
On Thursday (10/01/2015 at 06:27PM -0500), drlegendre . wrote:
> Now a question..
> Can someone give me a quick rundown on how the CPU communicates with this
> board? Does the board show up as a few bytes in the memory map, like on
> page zero? Does it connect directly to some registers in the CPU? How does
> data move from the CPU / buss into & out of the board?
> In short, how does the computer know where to "find" the board - and how do
> they converse? I'm only concerend with the serial portion, the rest is
> still a mystery - the 50 pin headers might be anything from parallel ports
> to (proprietary?) controller interfaces.
This is where I'm holding onto my theory that it is a custom design for
a specific purpose-- as I do not see the usual jumpers or DIP switches
to set I/O or memory addresses. If it were a generic card built for
general purpose use, it would almost certainly have DIP switches to set
an I/O or memory address decode.
On S-100 systems, you have both I/O and MEMORY space. Things like serial
port cards were almost always in I/O space and were decoded within a 256
byte block. Different S-100 systems had their console or other I/O at
different addresses and with different chips (8251, 6850, 2661 and other
UARTs with internal register sets as well as TR1602, AY-3-1015 and similar
Without any jumpers or switches to set the decode, you will have to
reverse the design to figure out how they did it. It might be I/O
mapped but it might be memory mapped since it was likely purpose built
for a specific application. Along with this, you will probably not have
operating system support that understands how to talk to this setup so
you will need to modify a CP/M BIOS or other OS I/O support to understand
how to talk to it.
The AY-3-1015 UARTs are "dumb". Their framing format is decided by
strapping inputs to the chip and then they present a byte-wide input
register and output register and strobes to read or write those registers.
This would likely be handled by buffers with enables to gate these paths
onto the S-100 bus.
I concur with Chuck that there were and are a lot of "MCT" companies.
I just have a high confidence that the logo on Bill's board matches the
logos I am familiar with for the local MCT here in town.
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