Rockwell Automation 1746-XXXX SLC 500 4-Channel Analog I/O Modules User Manual - Manual (Page 47)

Publication 1746-UM005B-EN-P - June 2004
Module Operation and System Considerations 4-9
System Considerations This section describes the system considerations for an analog
module. These include:
•
safe state for outputs
•
retentive programming
•
input out-of-range detection
•
response to slot disable
•
input channel filtering
Safe State for Outputs
Whenever an SLC 500 system is NOT in the RUN mode, the outputs
on the analog module are automatically forced to 0 Volts or 0 mA by
the SLC 500 system. This occurs when the processor is in the:
•
FAULT mode
•
PROGRAM mode
•
TEST mode
Retentive Programming Option
This section describes the affects of a processor mode change on
analog outputs. The following information applies to the 1746-NIO4I,
NIO4V, NO4I and NO4V analog modules.
This programming option allows you to retain analog data in the
Input and Output Image tables when the SLC 500 processor:
•
transitions from RUN-PROGRAM-RUN mode OR
•
when power is turned OFF and reapplied
In both cases, when power is reapplied, the data is transferred to the
module whether the programming rung is true or false.
If an SLC 500 system detects a fault condition, the analog outputs reset
to zero. The data in the Output Image table is retained during the
ATTENTION
When designing and installing the SLC 500 system,
devices connected to the analog module output
channels must be placed into a safe state whenever
the analog output is 0 volts or 0 mA (± the offset
error).