Measurement Computing CIO-INT-32 - Manual (Page 10)

The voltages and currents associated with external devices range from less than a
hundred mA at a few volts for a small flash light bulb to 50 Amps at 220 volts for a
large electric range. Attempting to connect either of these devices directly to the
CIO-INT32 would destroy the I/O chip.
In addition to voltage and load matching, digital signal sources often need to be
de-bounced. A complete discussion of digital interfacing will be found in the section
on Interface Electronics in this manual.
IMPORTANT NOTE
The Z8536 digital I/O chip initializes all ports as inputs on power
up and reset. A TTL input is a high impedence input. If you
connect another TTL input device to the Z8536 it will probably be
turned ON every time the Z8536 is reset, or, it might be turned OFF
instead. Remember, and Z8536 which is reset is in INPUT mode.
To safeguard against unwanted signal levels, all devices being controlled by an Z8536
should be tied low (or high, as required) by a 10K resistor.
You will find positions for pull up and pull down resistor packs on your CIO-INT32
board. To implement these, please turn to the section on pull up/down resistors.
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