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w hich is not installed in the PIO 4 board.
four input ports were installed, the 5 volt power that could
be drawn from the connectors would raise from 300 to 500
milliamperes.
INTERRUPT SELECT JUMPER SOCKET
Position C2 on the PIO 4 board is the interrupt select jum
per socket.
eight of the priority interrupt lines for the IMSAI 8080,
the four input interrupt lines and the four output interrupt
lines of the PIO 4 board.
to be used may be jumpered from the appropriate pin as noted
on the diagram below.
If an interrupt is desired to be used, the jumper m a y be
put between the interrupt line from the desired input or
output port to the desired priority interrupt on the IMSAI
8080 back plane.
monitor these interrupt lines and originate the interrupt
to the processor according to which line is requesting an
interrupt.
at the same time, the higher priority line rules.
example is shown below for connecting the interrupt line
from input port
line from output port
8
22
Appearing at the pins of this socket are all
The IMSAI PIC
If more than one line is requesting an interrupt
to level 5 priority and the interrupt
2
to level
2
PIO 4, Rev. 2
User Guide
Thus, any interrupt line desired
board must be used to
- 8
priority interrupt.
2
For example, if
An
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