TI-H: RS232 emulation on the link port

[Prev][Next][Index][Thread]

TI-H: RS232 emulation on the link port

Everyone discusses the possibility of using a Graph Link to hook a modem
to a TI and a program such as Talk-85 or (the currently nonexistant?)
ZTerm. I know this has been discussed before, but I think it should be
possible to emulate the TxD and RxD lines with the link port using just
software. It won't be easy, but maybe you could use the self-counting R
register, which is normally used as a memory refresh counter in the Z80
processor, as a sort of timer?


I've calculated the clock frequency of my (unturboed) TI to be about 6,3
MHz with a ZShell program. I estimate it would be possible to make the
link port work as fast as 9600 bps with only software on an unturboed
calc, maybe even more (14400, 19200 bps) with skillful programming.
After the IR link is completed (I cooperate with Keith Burzinski to make
it) I might start making a RS232C emulator terminal program.


I need some information though: Does anybody know how long a M1-cycle is
compared to a clock (T) cycle? Some books say it's 4 T-cycles, but the
datasheets show it can't be exactly that. Maybe around 3,5?
Actually, the question is how many M1-cycles an unturboed TI-85 executes
per second. Does anyone know?


-Ozone


<pre>
---
*** Osma Suominen *** <a href="mailto:ozone@clinet.fi">ozone@clinet.fi</a> *** http://www.clinet.fi/~ozone
***
</pre>