National Instruments NI PCI-8254R - Manual (Page 14)

Chapter 2 Digital I/O
© National Instruments Corporation 2-3 NI PCI-8254R User Manual
Isolated Inputs and Outputs
The isolated inputs and outputs on the NI 8254R have a separate ground
reference from the main NI 8254R device supply, providing an easy means
to prevent ground loops that can introduce noise into a system. You can
apply signals up to 30 V to the isolated inputs. The voltage swing of the
isolated outputs is determined by the voltage you supply on the 2-position
isolated outputs power connector.
Note V
iso
is referred to as V, and C
iso
is referred to as C on the 2-position isolated outputs
power connector on the NI 8254R.
Note The isolated outputs have current-limiting protection circuitry. If this circuitry is
tripped, you can re-enable the outputs by removing the fault and restarting your computer.
Watchdog Output 1 TTL Output 0 3 4
General
Purpose Output 3 TTL Output 5
TTL Output 6
TTL Output 7 19
21
22 21
23
24
* TTL Input 0 and TTL Input 1 can also function as trigger change detectors.
Table 2-1. NI 8254R TTL Inputs and Outputs (Continued)
Primary
Function
Input
or
Output
Number
Available Signal Names
44-Pin
D-SUB on
NI 8255R
Device Pin
Number
37-Pin
Terminal
Block
Number