Date   : Fri, 08 Feb 1991 20:41:00 CST
From   : LANCE TAGLIAPIETRA <TAGLANCE@ucs.UWPLATT.EDU>
Subject: Is my machine too SLOW for 2400bps modems?

>Darrell Pittman <pittman@mwk.uucp> writes
>
>In article <316@fxrs.intel.com>, jmasters@fxrs.intel.com (Justin Masters)
write
   s:
>
>> I'm using Qterm 4.2f and I've also used MEX 1.12 (or some old version like
>> that).  Both worked beautifully for me when I had 1200 baud capability, but
>> now it seems that 2400 baud is too fast.  Is this true?  How do I fix
it?  Is
>> it a problem of my machine waiting too long at the end of the line before
>> continuing on to the next line?
>
>    The video driver on your machine is probably too slow in scrolling the
>screen up when it receives a line feed.  Probably the only thing you can do
>is to get the remote system(s) to send you a certain number of NULL characters
>(ASCII 0) after each CR/LF.  Most BBSs have that capability.
>
 
This is exactly what is happening. The serial port is ignored
when the screen is being scrolled. Fortunately there is a
solution to this problem. There is an overlay for MEX version
1.14 for the TRS-80 Model 4 which is interrupt driven. The
interrupt routine runs asynchronously from the modem in routine,
deposting characters into a buffer. The modem in routine which
MEX calls, grabs characters from the buffer.
 
The overlay is available in the MEX area of the cp/m file section
on simtel, under the filename MXO-RS32.ASM.  There are earlier
overlays for the model 4 available, but these do not use the
model 4 interrupts.
 
Hope this helps,
 
Lance Tagliapietra  taglance@ucs.uwplatt.edu or taglance@uwplatt.edu