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Set of Apple II Hard Drive Images
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AEPC:DRIVERS
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README2.txt
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2020-08-13
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83 lines
Many PC telecommunications programs do not work on the PC
Transporter, for example Telix 3.12. Usually they lock up
shortly after they are started. There was a communications
program I wished to use called SIMPC. It did not work on
the PCT so I investigated and found the problem was that
too many "transmitter empty" interrupts were being generated.
On a real IBM PC when a character is sent to the modem the
serial port will generate a single transmitter empty interrupt
after it has finished sending the character. When the next
character is sent it generates another interrupt etc. On
the PC Transporter, however, transmitter empty interrupts are
generated continuously as long as the transmitter is empty.
This is several hundred interrupts a second.
Attached is a small basic program that will patch the SSCCOM1
interrupt handler so it only generates one transmitter empty
interrupt per character sent. A version of this fix for the
GSCOM1 driver has been tested and all telecommunications programs
I have that failed to work previously now work fine, including
SIMPC and Telix 3.12. I have been told that Telix 3.11 fails
to work with this patch applied.
Put the Applesoft basic program SSCCOM1.FIX on a disk or in a
subdirectory. On the same disk or in the same subdirectory
put a copy of the SSCCOM1 driver from the AEPC.DRIVERS
subdirectory and rename it to SSCCOM1X. Run the program
SSCCOM1.FIX and it will patch SSCCOM1X. Put the patched SSCCOM1X
into the AEPC.DRIVERS subdirectory, run PC Transporter, get
into the PCT Control Panel main menu and rebuild your config-
uration, using SSCCOM1X instead of SSCCOM1. The version number
of SSCCOM1X has been changed from v1.3 to v1.X so you can be
sure you have the new version.
NOTE: When configuring the driver you can no longer use
the "Use Settings from PC Transporter Menu" under
the "Data Length, Stop Bits, and Parity Menu". I
had to put the new code somewhere so I replaced the
code that handles this option. I use "Use Settings
from 8086" on my PCT.
Thanks to Chris Hays for testing this patch. I don't have a
Super Serial Card but a similar patch for the Apple IIgs
GSCOM1 driver has been tested and it seems to work fine for me,
but I cannot guarantee it will work for everyone. Also,
presumably the other drivers in the AEPC.DRIVERS subdirectory
have the same bug but I only have a IIgs so I cannot patch
or test the others. I have passed this information along to AE
and hopefully they will fix all the drivers.
For those who prefer to use a block editor this is what the
basic program patches: (all values in hex)
At offset 75B in SSCCOM1 replace 33 with 58
80B replace 8D 37 1D with 20 54 18
853 replace
AC 3B 1D AD 42 1D 38 6A 6A 6A 6A 0D
43 1D 99 8B C0 AD 44 1D 4A 6A 6A 6A
09 0B 99 8A C0 4C 86 18
with
00 8D 37 1D 8D 53 18 60 EE 53 18 AD
35 1D 60 AD 53 18 D0 03 4C D0 1C CE
53 18 A9 02 4C DE 1C EA
8E0 replace AD 35 1D with 20 5B 18
CCC replace A9 02 D0 0E with 4C 62 18 EA
Hugh McKay
Compuserve: 76505,311
Genie: HR.MCKAY
Bix: hmckay