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KAYPRO
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DUALPORT.LBR
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DUALPORT.DOC
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2000-06-30
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DUALPORT.DOC
Using Kaypro's to demo software
02/22/84 D. Berg
Recently I was asked if there was a way to set up multiple
displays using Kaypro computers at the user group meetings. One
computer was to run a software demo and the other units were to
simply display a copy of what was on the main unit. After giving
the problem a little thought this is what I came up with.
First a program would be needed in the main "demo" unit to
catch the characters going to the screen and pass them to the
serial port where the remote displays could read them. This
program would need to fit in the machine in a manner such that it
would not interfere with normal operations - but would catch
everything going to the screen. Then a cable(s) would be needed
to connect the main unit with the display units. And finally the
display units would need to have a terminal program running in
them - like TERM.COM.
Operating procedures for the setup above are as follows:
The computers are set-up and connected with the cable (described
later). The baud rate would be set to 9600 baud and the TERM
program run. These units will now function as display monitors.
The main-demo unit is booted and the DUALPORT program run. It
sets the unit to 9600 baud and patches the I/O to go to both the
screen and the serial port. DUALPORT will remain in effect until
the system is powered off or the reset button is pressed. CTRL-C
will not affect the operation however.
The cable needed in this setup is simple requiring only two
wires be hooked up between the units. Refering to the diagram
below the HOST unit is the main demo unit and the REMOTE unit is
the display units. Multiple display units can be connected in
parallel qith each other. There is a limit to the number that
will work but it should handle up to 6 units. On all connectors
pins 5, 6, and 8 are connected together on that connector only.
Pin 7 of all connectors are connected together in parallel. Pin
2 of the HOST connector is connected to all pin 3's of the remote
connectors. This forms a one-way communications link from the
HOST to all the REMOTE units.
HOST REMOTE
-------- --------
1 1
2--------------+ 2
3 +---------+-------3
4 ! 4
*---5 ! 5---*
*---6 ! 6---*
! 7--------------------+-- ! ------7 !
*---8 ! ! 8---*
V V
To other REMOTE
display units.