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IRQ's continued

To: <ct-user@contesting.com>
Subject: IRQ's continued
From: hatcher_d@bt-web.bt.co.uk (hatcher_d)
Date: Fri, 8 Apr 1994 10:47:10 +0100
IRQ's Continued, my two pennies ...

My experience using CT's COMTSR's and CT networking relies
on each serial port having its own IRQ line (which you set
when you load the COMTSR). If this is not the case, data can 
be lost when multiple lines have CT network traffic at the 
same time (the first raising of the IRQ gets serviced - the
others are lost, hence possibly the data as well).

As has been said, you can hard wire cheap 2 port serial cards
to any IRQ you like - I have seen many that can only support
IRQ 4 or 3, but it's straight forward to re-wire them and save
a bundle in the process. I was lazy and got a 4 port serial
card to start with. Has anyone experimented with some of the
cheaper 8-port cards?

A good book I found describing both ISA and MCA mechanisms
as well as source code to drive them in C++ can be found in
"Serial Comms Programming, a C++ development guide" by
Mark Nelson, M&T Publishing. Its pretty down to earth and
quite readable (for a change).

As an aside, I thought about writing a COMTSR-like device
driver for NE1000/NE2000 ethernet cards. If using a single 
"COMx" to an ethernet card, you wouldn't need more than one
virtual port for all CT network traffic - hence no more 
IRQ hunting.  

The only down-side is that stray RF is probably much more 
likely to get into a long length of ethernet cable than 
lengths of serial cable. I'd still probably have a go if 
the specs for the COMTSR's were publicly available. Anyone 
got thoughts on this?

= Darren Hatcher - G7BKO               =
= Packet   : G7BKO @ GB7DXM.#36.GBR.EU =
= Internet : hatcher_d@bt-web.bt.co.uk =
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