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PCJR9600.DOC
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1987-08-10
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PCJR9600
A program for enabling the IBM PCjr
serial port to operate at 9600 baud
By Gary Strait Poughkeepsie, NY
Version 3.10 August 9, 1987
PUBLIC DOMAIN This program is contributed to the public
domain, and may be distributed and used freely provided
that no fee is charged for its distribution or use and
that it is distributed only in a complete and unmodified
form, including these instructions.
This program was written to enable X*PRESS and X*CHANGE cable
services to operate on the IBM PCjr.
This program is necessary since X*PRESS and X*CHANGE use a
BIOS interrupt call to set the serial port to 9600 baud so
that it can receive the 9600 baud data feed, but PCjr BIOS
does not support 9600 baud. This program is a replacement
for the section of PCjr BIOS that sets the serial port baud
rates.
This program will also enable any other program or function
(including the DOS mode command) that uses this BIOS call to
select 9600 baud on the PCjr. Note that some programs
(examples: PROCOMM, QMODEM) do not use this BIOS function,
so they are able to set 9600 baud without PCJR9600.
The PCjr cartridge basic cannot handle 9600 baud. PCJR9600
will not change this.
To install this program, simply type PCJR9600 at a DOS
prompt; or if you want to always run with it installed,
include PCJR9600 as a line in your AUTOEXEC.BAT file.
There is no reason you could not have it installed at
all times; it only consumes a few hundred bytes and
still allows other baud rates to be used.
When run, this program installs itself permanently in
memory, ready to handle the BIOS function calls for
the serial port. It will remain resident until you
power off or re-boot DOS. (Don't install it more than
once, or you will have multiple copies in memory,
wasting memory space)
No messages appear on the screen when PCJR9600 is loaded,
nor are the baud rates of the serial port or internal
modem port changed. X*PRESS and X*CHANGE will call the
PCJR9600 code (in memory) to set 9600 baud when you start
them up. If you're running some other software that does
not automatically set the baud rate for you, you can
use the DOS MODE command to set the serial port or
internal modem port to whatever is required.
Hints for running X*PRESS or X*CHANGE on the PCjr:
- PCJR9600 must be loaded BEFORE you start the X*PRESS or
X*CHANGE software.
- You will need at least 256k bytes of memory. The more
the better. 640k would be best. The more memory
you have, the more stories you will be able to select
from at any one time. (X*PRESS and X*CHANGE store all
the incoming data in memory, as much as you've got room
for, and let you select from whatever is in memory)
- Make sure the DOS disk you use does whatever is necessary
to use the additional memory. IBM memory attachments
require a CONFIG.SYS file with a DEVICE=PCJRMEM.COM
statement (optionally followed by a /C or /E). Most
other add-on memory attachments require a similar
procedure.
- You will need the PCjr adapter cable for serial devices
to connect the signal to the PCjr if you will be using
the built-in serial port. There are also add-on serial
ports available. For example, Legacy Technologies makes
one that fits the internal modem slot. If you're using
something like this, make sure it has a DB25 (25 pin
D-shell) connector.
- If the X*PRESS or X*CHANGE receiver is connected to your
PCjr when you power on or re-boot, you may get an ERROR D.
If you do, just press enter to continue. This is not a
hardware failure. If the power-on self test sees data
incoming from X*PRESS or X*CHANGE when it is trying to
test the serial port, it thinks the serial port is broken.
The power-on self test was written assuming the PCjr compact
printer or a modem would be connected. Neither of these
would be sending data to the PCjr during this time.
- Set MODE CO80 or any other 80 column mode before starting
X*PRESS or X*CHANGE. These programs will not work in
40 column mode.
- Data is constantly being received. Display updates,
keyboard input, and disk drive accesses can cause the
PCjr to not keep up with the incoming data. These should
be avoided as much as possible to get the maximum amount
of data. Turning off the feed ticker (one of the PC
Setup options in the X*CHANGE MENU) cuts down on a lot of
display updates. I recommend turning it off.
- If you're using an IBM memory expansion attachment and at
least 384k, you can change the DEVICE=PCJRMEM.COM statement
in your CONFIG.SYS file to DEVICE=PCJRMEM.COM /C. This
will make the PCjr run faster, but will reduce the amount
of memory available. Or, you can set up a RAM disk to
fill all of the lower 128k of memory not being used for
the video buffer or DOS. (This same trick can also be
used to speed up the PCjr for many other programs) This
works because the memory built into the PCjr runs slower
than external add-on memory attachments, and doing either
of these things forces programs to run in the external
memory.
- If you have an internal modem or a serial adapter in the
internal modem slot, you're all set. Just select the
secondary communications adapter in X*CHANGE if you're using
built-in serial port, or the primary communications adapter
if you have the X*CHANGE receiver connected to a serial
adapter in the internal modem slot. If you don't have one
of these devices in the internal modem slot, you may need
an extra step to get X*CHANGE running. Start X*CHANGE and
select the secondary communications port (from the PC setup
option in the main menu). If you don't get any data, exit
X*CHANGE and re-insert your DOS disk. Enter the following
command:
MODE COM1:9600,N,8,1
Restart X*CHANGE, and you should now receive data. You
will need to issue this command each time you re-boot.
This is necessary because the PCjr hardware doesn't work
quite the same as other PCs if the internal modem is not
installed.
To make startup easier, you can put this command in your
AUTOEXEC.BAT file. Put it AFTER the PCJR9600 statement.
- The X*CHANGE people told me that their kit would not work
on the PCjr (it doesn't without this program). They didn't
want to send it to me at first, thinking I'd not be able to
make it work. I've told them I did get it to work, so they
may not object to orders for the PCjr in the future. (they may
even change their program to work on the PCjr, since I told
them that it could be done). Be sure to tell them you're
connecting it to a PCjr when you order, so you get the correct
cable to fit your serial port. They have different cables
depending on what type of computer you're connecting to.
Also note that if you have an add-on serial port, it may
not have the same kind of plug as the IBM PCjr adapter cable
for serial devices. If you are using one of these devices,
make sure you tell X*PRESS so you get a matching cable.
Also tell them what cable TV company you're on. Different
cable systems require different receivers.
What are X*PRESS and X*CHANGE?
X*PRESS and X*CHANGE are 2 different (but similar) services
offered by X*PRESS Information Services, Ltd. They are
based in the Denver, Colorado area and send data by satellite
to participating cable TV systems. The cable systems broadcast
the signal over their cable lines to receiver boxes in the
users homes. When you order their service, you get a receiver
box that goes between the cable TV line and the serial port of
your PC. You receive a 1-way transmission containing news,
sports, and weather stories, and stock prices for North American
stock exchanges. Excerpts from Byte magazine are also carried.
X*PRESS Executive (one of the services) also provides additional
financial and business news and news for each of the 50 states.
X*CHANGE (the other service) has less frequent stock updates
and less financial and business news, but adds home shopping,
lifestyles (recipes, articles on food, fitness, money management,
families, careers, etc.), entertainment (TV schedules and movie
and book reviews, horoscopes, etc.), and user conferences.
If you don't know if your cable company carries these services,
ask them, or ask X*PRESS information services. Their phone
number is 1-800-446-4266.
This program has been tested on 3 different PCjrs and works
on all 3, but I cannot guarantee that 9600 baud will always
work with a minimal error rate in all circumstances.
Remember, IBM says 9600 baud is not supported in the PCjr,
so if it doesn't work reliably enough for you, IBM won't
fix it.