Re: TI-H: TI-Modem one big reply

To: ti-hardware@lists.ticalc.org
Subject: Re: TI-H: TI-Modem one big reply
From: Osma Suominen <ozone@clinet.fi>
Date: Fri, 08 Aug 1997 21:06:40 +0000
References: <Pine.GSO.3.95.970807202255.28025C-100000@chaos.cns.uni.edu> <33EACBC1.80416A8F@jhs.net>
Reply-To: ti-hardware@lists.ticalc.org

Ben Shakal wrote:
> 
> What ever happened to that single-chip 300-baud modem?  I know 300 isn't
> much, but it might be worth the sacrifice in speed for its small size
> and low price.  It is National Semiconductor part no. MM74HC943N (I
> think... that might be the wrong one).  And it could even be built using
> that SPinTerface cartridge system. :)

Too bad you can't hook the MM74HC943N directly to the link port. You
need a serial port. That can be done with a UART such as Philips'
SCC2691 (it has only 24 pins and a 4-byte FIFO buffer to prevent
overflows), and that again can be connected with a multiplexing circuit
such as PCF8574 which connects to the I2C bus, which again can be
emulated by the TI link port. You need two PCF8574's to use the UART.
But I think this kind of system would be too expensive. It could,
howewver, theoretically reach at least 19200 bps, which the Graph Link
can't.

A PIC or similar microcontroller could, of course, also be used, but
it's not very easy to program.

-Ozone

-- 
*** Osma Suominen *** ozone@clinet.fi *** http://www.clinet.fi/~ozone
***