Rockwell Automation 1771-TCM TEMPERATURE CONTROL - Manual (Page 9)

1–2 Interfacing with the Temperature Control Module
Publication 1771Ć6.4.5 - January 1997
The sample ladder logic can be combined with the other logic you
need for your application. If you prefer to write your own ladder
logic, it must duplicate the arrangement of data within the block and
the operation of the control bits that the sample logic uses in order
for the configuration software to operate correctly.
During installation of the configuration software, you will have the
option of copying the sample ladder logic to your computer. From
there, you can restore the program to your processor using your PLC
programming software. You then edit the subroutine in the sample
ladder logic so that the block transfer instructions address the correct
rack, group, and slot for your module. You also edit the subroutine
to use your desired data table block address.
If you have multiple modules, you make a copy of the subroutine for
each module, and then edit the copies as described above. Refer to
Appendix C of the Temperature Control Module User Manual
(publication 1771-6.5.120) for detailed instructions on editing the
sample ladder logic.
The Temperature Control module communicates with the PLC
processor by both block-transfer and single-transfer. The ladder
logic must include block-transfer write instructions to send the
following data blocks to the module:
•
a configuration block for each PID loop (8 max)
•
gains block
•
auto-tune block
•
dynamic block
•
calibration block (not required for normal operation)
The ladder logic must include block-transfer read instructions to get
the following data blocks from the module:
•
system status
•
gains block
•
auto-tune block
•
calibration block (not required for normal operation)
Unless the 1771-TCM module is located in a remote I/O chassis, you
can provide high-speed processing of time-proportioned output
(TPO) signals by including instructions in the ladder logic for
dealing with an input image byte single-transferred from the module.
This byte contains the control-variable output of each loop as the
duty cycle of a bit that is cycled at a regular period. Each bit
represents one of the 8 PID loops.
Using the Sample Ladder
Logic Program
How the Temperature
Control Module
Communicates with PLC
Processors