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FUNCTIONAL DESCRIPTION
The PI06 Board provides the IMSAI 8080 Microcomputer System with
two sets of 24 parallel programmable I/O lines and the capability
of extending its own standard I/O bus to peripheral devices.
Each set of 24 parallel I/O lines is derived from Intel's 8255
programmable peripheral interface integrated circuit.
of the PI06 Board is that of a general purpose I/O component to
interface peripheral equipment to the IMSAI 8085 Microcomputer
System bus.
e The functional configuration of the PI06 Board is controlled by the
Sfsmicroprocessor software.
§?^grammable in two groups of
?i*operal
i:
A3 —
Mode O - Each group of 12 I/O pins may be programmed
Mode 1 - Each group of 12 may be programmed to have
Mode 2 - Bidirectional bus mode which uses eight lines
The control lines of the 8255 chips are also brought to PI06
connector pins (in J2 and J3) for additional control by the
peripheral device.
Enough microprocessor control and bus signals are brought through
the PI06 Board connectors J2 and J3 so that the "Isolated I/O"
technique directly from the processor can be implemented in the
peripheral device.
"Memory Mapped I/O" technique directly from the microprocessor can
be implemented in the peripheral device.
lines from the microprocessor.
so that interrupt lines from the 8255's can be directly jumpered to
the processor's vectored interrupts.
Connection to the input or output ports is made through board edge
connectors at the top of the board on
fingers will accept
other
inch center to center board edge connectors.
0 . 1
The board uses a 7805 integrated circuit regulator for the +5 volt
power and tantalum capacitors before and after the regulator with
ample ceramic disk capacitor bypassing throughout the board.
The twenty-four 8255 I/O pins are pror*
each and used in three basic modes of
1 2
in sets of four to be input or output.
eight lines of input or output.
remaining lines in each group are left for
"handshaking" and interrupt control signals.
for a bidirectional bus, and five lines,
borrowing one from the other group, for
"handshaking".
With the addition of J4 to the PI06 Board, the
Pads are provided on the PI06 board
3M flat cable edge connectors as well as
PI06
Functional Description
Revision O
The four
J4 also provides interrupt
inch centers, and the
0 . 1 0
The function
most
1
3
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