Advertisement
Each of the data input lines on the input ports is tied to
+5 volts through a IK resistor so that unused lines will
be read as high data level or true data level.
As an alternative, two EIA type connectors, 25 pins each,
may be connected by way of flat cable and the 3M flat
cable system to the board, so that the. board connections
can be taken to the EIA connectors with no hand wiring.
This is true of the input port connector and the output
port connector.
The connectors are arranged so that if the EIA 25 pin
connectors are used, either two output ports or two input
ports appear on the pins of the EIA connector along
with both ground and +5 volts.
each needing only one output port, they may be connected
without hand wiring both to the EIA 25 pin connectors by
passing the flat cable through the first connector into
a second so that two 25 pin connectors can be connected
to the same flat cable; then only one port would be used
in the first connector
in the other connector.
from separate peripheral devices without requiring any
hand wiring of cables.
the input ports.
If desired for custom program display front panel-type use
or just debugging use, the user can assemble the output
ports with
LED's and current limiting resistors of
8
either 220 or 330 ohms, so that the user has a visual
indication fo the status of the output bits.
If the PIO 4 board is to be used in place of the front panel
for custom program output, care should be taken during
assembly to make sure that the disk ceramic bypass capa
citors are not stood up but rather are laid over on top of
the resistors they are next to so that they do not extend
higher than the LED's.
The L E D 's on the output ports are turned on when the data
bit is written as a 0.
it was a more cost-effective solution for the user to put
a complement instruction in his/her firmware than it was
for IMSAI to put inverters in the hardware.
The +5 and ground pins on the input and output port con
nectors can be used to provide 5 volt power at up to 200 or
300 milliamperes total from the full board.
approximately
1 0 0
power would be available for each 8212 input or output port
If there are two devices,
and the other port would be used
This would permit separate plugs
The same, of course, is true for
This was done because it was felt
additional milliamperes of
PIO 4, Rev. 2
User Guide
In addition,
volt
+ 5
8 - 21
Advertisement
