Manual

Communicating with Your Module
Chapter 3
3-4
TPO Bits
The loop designations of the heat/cool (control-variable) TPO bits in the
high byte of the input image word are as follows.
76543210
Loop 1
Loop 2
Loop 3
High
byte of input image word (heat/cool
TPO bits for control variable)
Loop 4
Loop 5
Loop 6
Loop 8
Loop 7
Controlling Heating Elements Only
In applications where the control variable TPO of each loop is used for
only heating, the ladder logic for data single-transferred to/from the
1771-TCM module must do the following:
Write the decimal value 35 (binary 00100011) to the high
byte of the output image word of the 1771TCM module.
Read the low byte of the input image word of the
1771TCM module.
If the low byte of the input image word of the 1771TCM
module has the value 35
10
, move the value from the high
byte of the input image word of the 1771TCM module to
the output image byte of the output module driving the
heating elements.
If bit 0 (watchdog timer) of the low byte of the input
image word of the 1771TCM module off , zero the output
image byte of the output module driving the heating
elements.
If bit 0 (watchdog timer) of the low byte of the input
image word of the 1771TCM module on and the low
byte of the input image word of the 1771TCM module
does not have the value 35
10
, do not write to the output
image byte of the outputs driving the heating elements.
High byte of 1771TCM
output word
Low byte of 1771TCM
input word
High byte of 1771TCM
input word
Heatingelement outputs
Heatingelement outputs
35
10
?
35
10
00000000
2