13
Chapter
13–1
The Force Function
This chapter briefly describes the force function. Topics include:
•
forcing I/O
•
forcing an external input
•
searching for forced I/O
•
forcing an external output
•
forces carried offline
The force function allows you to override the actual status of external input
circuits by forcing external input data file bits On or Off. You can also
override the processor logic and status of output data file bits by forcing
output circuits On or Off.
You can install and then enable or disable forces with the processor in any
mode while monitoring your file online.
To force an external input, the following program (the same program used in
the last chapter), is used throughout this chapter.
Operation:
This program is used to achieve the maintained contact
action of an On-Off toggle switch using a momentary contact push
button. (Press for on; press again for off.)
The first time you press the push button (represented by address
I:0/1), instruction B3/11 is latched, energizing output O:0/0. The
second time you press the push button, instruction B3/12 unlatches
instruction B3/11, de-energizing output O:0/0. Instruction B3/10
prevents interaction between instructions B3/12 and B3/11.
Note:
If you have not yet entered this program and downloaded, refer
to chapter 10.
The controller configuration and
I
/
O
addresses
programmed in the HHT must match the controller you download to.
This program is written for a fixed controller.
]/[
B3
10
0
] [
1
( )
B3
11
( )
B3
12
1
] [
B3
11
]/[
B3
12
]/[
B3
10
( )
O:0.0
0
( )
B3
10
] [
1
] [
B3
11
2
3
] [
B3
11
] [
I:0.0
1
I:0.0
I:0.0
Forcing I/O
