Timer and Counter Instructions
Timers and counters control operations based on time or the number of events.
Bellow commands that can be used in ladder diagram
| TON | TOF | RTO | CTU | CTD | RES |
Bellow commands that can be used in Function Blocks and Structured Text
| TONR | TOFR | RTOR | CTUD |
Commands Description.
| If you want to | Use this instruction |
| time how long a timer is enabled | TON |
| time how long a timer is disabled | TOF |
| accumulate time | RTO |
| time how long a timer is enabled with built-in reset in function block | TONR |
| time how long a timer is disabled with built-in reset in function block | TOFR |
| accumulate time with built-in reset in function block | RTOR |
| count up | CTU |
| count down | CTD |
| count up and count down in function block | CTUD |
| reset a timer or counter | RES |
The time base is 1 msec for all timers. For example, a 2 second timer’s .PRE value should be 2000.(For Control Logix PLC)