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1990-10-28
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README.DOC for SETCOM40.SYS
by John W. Cocula
October 28, 1990
Description
-----------
(Recently, I replaced an 8250 UART on my serial card with a 16550AFN
chip. Now the chip is not recognized on a warm boot, and COM01.SYS
won't install for it. I have to hardware reset to have the port
recognized. This is what I did about it.)
SETCOM40.SYS is an OS/2 device driver which serves a very specific
purpose: it sets the COM ownership words in the BIOS data area to
either the defaults:
COM1: Port 3F8
COM2: Port 2F8
or to parameters passed in on the device driver's "command line" in
CONFIG.SYS.
The point of this driver is to override what the computer's BIOS
discovers during its self-test during boot. One reason to do this is
so that a NS16550AFN UART chip can be recognized by the COM01.SYS
device driver on machines with certain BIOSes (like my AMI BIOS). You
would install this driver *before* COM01.SYS (and serial mouse drivers)
to set up the COM ownership words.
I named the driver SETCOM40.SYS since it performs basically the same
thing that the OS/2 DOS box command SETCOM40 does, which fiddles with
these values at 0040:0000 in the BIOS data area.
***********************************************************************
*** If you don't understand any of this, don't install this driver! ***
***********************************************************************
Otherwise, put this driver somewhere on your disk and put the
following in CONFIG.SYS *before* your comm driver loads:
DEVICE=[drive]:[path]\SETCOM40.SYS [/COM1=addr of COM1] [/COM2=addr of COM2]
both [/COMn=addr of COMn] parameters are optional. If either is missing,
the defaults of 3F8 and 2F8 will be used for COM1 and COM2,
respectively. If present, they must be THREE HEX DIGITS each. Using
000 indicates that the port is not available. Also, currently all
alpha characters must be in UPPERCASE. This is laziness on my part.
Examples
--------
You have one serial port, and for some reason your BIOS does not recognize
it on a warm boot. Put this in your CONFIG.SYS:
DEVICE=C:\SETCOM40.SYS /COM1=3F8 /COM2=000
(Note that if you only have one serial port, you must specify /COM2=000
or you will unintentionally fool COM01.SYS into thinking you have the
hardware.)
You have two serial ports, and COM2 is not recognized on a warm boot:
DEVICE=C:\SETCOM40.SYS /COM2=2F8
or just
DEVICE=C:\SETCOM40.SYS
since the addresses are assumed.
Details
-------
This device driver does its thing at INIT time, but then serves no
other purpose. However, it does not uninstall, because OS/2 will pause
for drivers that fail to install. But fret not because it takes up
very little memory, and its device has the unlikely name of "SETCOM$$".
Feel free to improve this driver in any way you see fit. If you make
changes and post them on a BBS, all that I ask is that you indicate
clearly that what you are distributing is not what I originally
distributed.
I release this work as "freeware", where I retain copyright and
ownership, but ask for nothing in return. It is provided AS IS,
without warranty, either express in implied, including but not
limited to fitness for a particular purpose.
John W. Cocula
October 28, 1990