Date: Thu, 15 Sep 1994 11:10:02 +0800 (SST)
From: Loh Lian Seng <scip3041 AT leonis DOT nus DOT sg>
Subject: Problems with serial port interrupt handler
To: djgpp AT sun DOT soe DOT clarkson DOT edu

Hi,

I am trying to write an interrupt handler for the PC serial port.  I 
tried the following and have the system stopped on various errors eg.
"0x0d not installed" and "protection faults"

a.  install a real-mode interrupt using a real-mode callback iret wrapper 
for my handler writtened in C

b.  install a protected mode interrupt handler using a pm-iret-wrapper for 
my C handler

c.  install both the above, I read somewhere that it will save CPU time 
in that it does not have to switch modes during the interrupt ???

All 3 programs will crash out after a few characters received, with (a) 
being the most stable.  I also seem to get overrun errors on the receive. 
(c) doesn't seemed to work (double characters) as I believe that GO32 
will always call the rm-handler as well.

BTW, I went throught DJASYNC codes which installed a serial interrupt in 
rm as a TSR.  Is this the only solution ?

Thanks in advance for any help.