Rockwell Automation 1746-NR8 SLC 500 RTD/Resistance Input Module User Manual - Manual (Page 48)

Publication 1746-UM003A-EN-P
3-12 Preliminary Operating Considerations
The table below gives you the turn-on, turn-off, and reconfiguration times for
enabling or disabling a channel.
By writing to the status file in your modular SLC processor you can disable any
chassis slot. Refer to your SLC programming manual for the slot disable/enable
procedure.
Input Response
When an RTD slot is disabled, the RTD module continues to update its input
image table. However, the SLC processor does not read inputs from a module
that is disabled. Therefore, when the processor disables the RTD module slot,
the module inputs appearing in the processor input image remain in their last
state and the module’s updated image table is not read. When the processor
re-enables the module slot, the current state of the module inputs are read by
the processor during the subsequent scan.
Output Response
The SLC processor may change the RTD module output data (configuration)
as it appears in the processor output image. However, this data is not
transferred to the RTD module when the slot is disabled. The outputs are held
in their last state. When the slot is re-enabled, the data in the processor image
is transferred to the RTD module.
Description Duration
Turn-On Time The time it takes to make converted data available in the
data word and to set the status bit (transition from 0 to
1) in the status word, after setting the enable bit in the
configuration word. Requires up to one module update time plus 510 msec +
125 milliseconds x the number of unique input type and
excitation current combinations.
Turn-Off Time The time it takes to reset the status bit (transition from 1
to 0) in the status word and to zero the data word, after
resetting the enable bit in the configuration word. Requires up to one module update time.
Reconfiguration Time The time it takes to change a channel configuration if the
new device type and excitation current are a unique
combination. The enable bit remains in a steady state of
1. (Changing temperature/resistance units or data format
does not require reconfiguration time.) Requires up to one module update time plus 510 msec +
125 milliseconds x the number of unique input type and
excitation current combinations.