WARNING! Verify that the signal source really floating. Check it with a ohmmeter before risking the CIO-DAS80# and PC.
2.3.5 Fully Differential
A differential signal has three wires from the signal source. The signals are Signal High (CH# High), Signal Low (CH# Low) and Sig-
nal Ground (LLGND).
A differential connection allows you to connect the CIO-DAS80# to a signal source with a ground that is different than the PC ground,
but less than 10V difference, and still make a true measurement of the signal between CH# High and CH# Low.
EXAMPLE: A laboratory instrument with its own wall plug. There are sometimes voltage differences in wall GND between outlets.
2.3.6 Digital Inputs and Outputs
All the digital inputs and outputs on the CIO-DAS80# are TTL level. TTL is an electronics industry term, short for Transistor Transis-
tor Logic, with describes a standard for digital signals which are either at TTL low or TTL high; levels which are detected by all other
TTL devices. For a listing of the TTL level specifications for these digital lines, please see the specifications at the end of this manual.
There are three digital inputs and four digital outputs. The digital inputs are buffered by a register on the board. Each time the register
is read, the current high/low state of the digital I/O lines is obtained. The digital outputs are controlled by a register on the board and
are updated each time the register is written to. The lines are pulled high so a logical-one is read if no signal is connected to an input.
The digital lines also are used to control external EXP boards (all four outputs) and to trigger and gate A/D conversions (Digital In 1).
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