Hello,
I happen to be a owner of a certain YAMAHA - MSX2 computer.
It's quite an ordinary MSX2 and fully compatible with other MSX2-s, except
for one
special feature - it has a special NETROM (32KB) with a serial I/O device
connected
to the sideslot (pslot=3 and sslot=3, to be exact). That kind of MSXs with
NETROMs
were widely used in the former Soviet Union and they were integrated into
so called
"Classroom networks" (Max. 15 computers!).
As I only have that one MSX, I'm wondering now how to connect it to my PC
by using
that special serial port. The main problem is that there seems to be no
(useful) information
available about that hardware. I have found only some materials describing
the special
NETROM's bios functions and basic CALLs which are quite sophisticated and
assume,
for example, the teacher computer's permission for any communication. But
there's nothing
about the specific hardware and how to program it directly! I can't see any
other reason
for that except that this information must have been classified. Probably
it just wasn't
desirable if student could "disobey" the teachers veto and communicate with
other
computer anyway.
But, as there's probably no msx-networks functioning anymore, I wonder if
somebody
could help me on that matter. I would be thankful for any information!
Meanwhile I have conducted my own research and as my latest achievment I
was able
to send my first bytes ever from MSX directly to my PC's COM port. I used
for that a simple
routine I found when poking around the NETROM and self-made circuit to
convert the
msx serial signallevels (approximately -6V & 0) to RS232 (12V & -12V). I
don't know exactly
how does the NETROM's routine function though - I just discovered that the
seems to be
some intialisation through port #09 (OUT (09),A) and the output goes to the
port #0e.
But unfortunately I haven't been able to achieve the opposite - I don't no
how to receive
a byte (and also must I use I/O polling or is it interrupt driven etc.)
So, I hope that there's somewhere someone who knows something about that
issue!
There must be :-)
Greetings,
Andres
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