Rockwell Automation 1771-TCM,D17716.5.108 TEMPERATURE CONTROL MOD - Manual (Page 24)

Communicating with Your Module
Chapter 3
3-2
The low byte of the input image word is used both for single-transfer
and block-transfer. For single-transfer, you read this byte to determine
whether the high byte of the input image word contains heat bits or cool
TPO bits.
The high byte of the input image word is used exclusively for
single-transfer. This byte contains the control-variable output of each
loop as the duty cycle of a bit that is cycled at a regular period (TPO).
You read the control bits in the low byte to determine whether these bits
are for a heating function or a cooling function.
Your ladder logic must provide the proper sequence of block-transfer and
single-transfer communication with the module.
At initial start-up
1. Write (block-transfer) the configuration block for each loop to the
module
2. Write (block-transfer) the gains block to the module.
3. Write (block-transfer) the dynamic block to the module
4. Read (block-transfer) the system status block from the module
If you use the dynamic block to select auto-tuning, you then must
1. Read (block-transfer) the system status block from the module on a
regular basis (using a timer to trigger block-transfers) to determine
when the auto-tuning is complete
2. When auto-tuning is complete, write (block-transfer) the dynamic
block to the module to remove the auto-tuning selection
3. When auto-tuning is complete, read (block-transfer) the gains block
from the module to store a record of the gains derived from
auto-tuning
4. Whenever there is no block-transfer in process for the temperature
control module, pass the single-transferred TPO of each loop on to
the output module driving the heating/cooling elements
After initial start-up and auto-tuning
1. Write (block-transfer) the dynamic block to the module whenever
necessary to change mode
Communication Sequence