Microport V/AT 2.4 at 19200 with Telebit Trailblazer

[Bob Thrush]

In article <1989Sep24.135744.5857 at trevan.uucp> trevor at trevan.uucp (Trevor J. Harris) writes:
>Is anybody runing a Telibit Trailblazer at 19200 on V/AT 2.4.
>I am not sure if the Microport drivers will support that speed so I was
>thinking about using the async driver posted to the net recently.
>I would be grateful for any advice

  I'm running V/AT 2.4, a TB+ at 19.2 kb, and HDB.  I would offer 
the following suggestions/recommendations:

  1. If you haven't already done so, replace the 16450 UARTs 
	 with 16550's.  
  2. Replace the Microport serial driver with the Murray driver.  
	 (It automatically detects the 16550 and uses the fifos.)
  3. Setup the TB to use hardware handshake (the Microport driver
	 does *not* support this.)  s58=2, s68=255 is what I use.

  The 16550 UART has a 16 byte receive and transmit fifo which
the Murray driver detects and uses.  On the receive side, this 
results in a significant reduction of the no. of interrupts serviced 
(from one per character to one per 14 characters).  It also reduces 
(in my case eliminates) character overruns.  On the transmit side, 
each time the output fifo is emptied an interrupt is generated and,
at interrupt time, the fifo (16 chars) is refilled.  This results
in fewer interrupts thereby reducing the interrupt load on the 
rest of the system.

  There was a cosmetic change I made to the driver to define
open_device() and close_device() static to match an earlier declaration.
I also changed the Makefile to additionally rm /dev/ttym[01] and
chmod 666 /dev/tty[01] and chmod 622 /dev/ttyM[01].

  This system is running a 10 Mhz 0ws 286 and is able (with no other
processes) to receive at peak rates of >1400 cps with an overall
average of about 1100-1200 cps.  The average modem traffic (for August) 
was ~20 Mb a day with a TB+ and a Hayes SM2400.

>			regards trevor
>-- 
>-------------------------------------------------------------------------
>Trevor J. Harris					ukc!trevan!trevor

-- 
Bob Thrush rd at aii.com or uunet!tarpit!rd 
Automation Intelligence,Inc.,1200 W. Colonial Drive, Orlando, FL 32804