Cromemco 8PIO This is an 8 port parallel I/O port
board. It was a natural evolution of their
4PIO board.
Each of the eight independent I/O ports
consists of a separate input port and an output port with the same port address.
Each input/output port pair share 8 bidirectional lines which are brought out to
EIA connectors (J1 thru J4) for I/O interfacing. Both the input and output ports
are latched: output data is automatically latched into an OUT port when the
system CPU executes an output instruction to the 8PIO. Input data is
latched into an 8PI0 IN port by a positive going transition on the LATCH INPUT
line which is controlled by the user. Handshake signals are provided on both the
IN and OUT ports.
I/O port number 6 plays a special role
on the 8PIO. It may be left in its factory wired condition to software monitor
and control the other seven 8PI0 ports, or alternately, it may be reconfigured
as a standard eighth I/O port. The 8PI0 provides three onboard terminal I/O
devices: an 8-bit switch register, a 3-bit switch register and an 8 LED
display register. The 8PI0 also features four versatile interfacing circuits: a
pair of OUT port activated relays and a pair of optically Isolated couplers
connected to an IN port. All of these devices are connected to the SPIO In a
non-dedicated fashion: they may be either used or left unused in a way that
leaves ail ports available for I/O with other devices .
