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From: cameronjames@snoc01.enet.dec.com (James Cameron)
Newsgroups: comp.sys.tandy
Subject: Re: Trash-80 model 100
Message-ID: <22238@shlump.nac.dec.com>
Date: 21 Apr 91 23:11:15 GMT
References: <1991Apr19.005102.10635@unicorn.cc.wwu.edu>
Sender: newsdaemon@shlump.nac.dec.com
Reply-To: cameronjames@snoc01.enet.dec.com (James Cameron)
Organization: Digital Equipment Corporation (Australia)
Lines: 35

In article <1991Apr19.005102.10635@unicorn.cc.wwu.edu>, n8643884@unicorn.cc.wwu.edu (peter c. vollan) writes:
>"M" indicates the internal modem, which is 300 bps only. Other settings are 
>speeds for data transfers, or external modeming, through the RS-232 cable.

I have a feeling the original poster was from New Zealand.  Be aware that the internal modem is built for the American market, and uses the BELL standard tones, rather than the international ones that everyone else uses.

>Next is an E or D, which is Enable or Disable handshake. I don't really 
>understand this one; perhaps someone can fill us in.

If set to D, then data will pass inwards without having CTRL/S and CTRL/Q filtered out by the RS-232C driver code, and if the buffer fills, nothing is done about it.

If set to E, then the driver will recognise incoming CTRL/S and CTRL/Q characters as transmission stop/start characters, and will not give them to the calling program (i.e. BASIC or TELCOM).  Also, (and here's the real neat thing), if the incoming buffer reaches around 75% usage, the driver transmits a CTRL/S character to the remote machine.  If it has done this, it won't transmit a CTRL/Q until the buffer usage drops to around zero.  [The actual percentages are coded into the ROM, and are probably not 75%








 and 0%, but something close to it... if you want to know the exact values I could look them up in my listing.]  The incoming RS-232 buffer is roughly 64 characters long, which is more than one line on the LCD screen.  The LCD is so slow in scrolling that it needs this buffer.

Basically, if you want to transfer stuff without translation and you are sure that the incoming buffer will not overrun, or if the remote machine gives you CTRL/S and CTRL/Q characters without reason, use D.

If you are using the Tandy 10x to talk to a larger machine, check to see if it responds to CTRL/S and CTRL/Q as stop/start requests, and if it does, then it is probably safe to use E instead.

Anotehr small point; if you type CTRL/Q in TELCOM when in E mode, a CTRL/Q is transmitted anyway.

>The number, 10 or 20, is the speed of the autodialer, which is rotary, and I
>hardly ever use it. 

International models do not accept this parameter.

>Also, what possible use could software to speed up the
>internal modem to 450 bps be? Am I missing something? 

Well, let's just say that I sped my 102's RS-232 up to 30,000 baud yesterday with no ill effects in order to control a MIDI synthesiser.  The theoretical maximum is 150,000 baud; but I can't vouch for how fast a machine coded routine could run to produce data.

As for 450 bps; dunno...
--
James Cameron
Digital Equipment Corporation (Australia) P/L
(cameronjames@snoc01.enet.dec.com)