Re_Trigr (Restart Cycle Monitoring Time) Instruction - Siemens S7-1200 System Manual

Basic instructions
7.8 Program control operations
7.8.6

RE_TRIGR (Restart cycle monitoring time) instruction

Table 7- 104 RE_TRIGR instruction
LAD / FBD SCL
RE_TRIGR();
Use the RE_TRIGR instruction to restart the scan cycle monitoring timer during a single scan
cycle. This has the effect of extending the allowed maximum scan cycle time by one
maximum cycle time period, from the last execution of the RE_TRIGR function.
Note
Prior to S7-1200 CPU firmware version 2.2, RE_TRIGR was restricted to execution from a
program cycle OB and could be used to extend the PLC scan time indefinitely. ENO =
FALSE and the watchdog timer is not reset when RE_TRIGR was executed from a start up
OB, an interrupt OB, or an error OB.
For firmware version 2.2 and later, RE_TRIGR can be executed from any OB (including start
up, interrupt, and error OBs). However, the PLC scan can only be extended by a maximum
of 10x the configured maximum cycle time.
Setting the PLC maximum cycle time
Configure the value for maximum scan cycle time in the Device configuration for "Cycle
time".
Table 7- 105 Cycle time values
Cycle time monitor
Maximum cycle time
Watchdog timeout
If the maximum scan cycle timer expires before the scan cycle has been completed, an error
is generated. If the user program includes a time error interrupt OB (OB 80), the CPU
executes the time error interrupt OB, which can include program logic to create a special
reaction.
If the user program does not include a time error interrupt OB, the first timeout condition is
ignored and the CPU remains in RUN mode. If a second maximum scan time timeout occurs
in the same program scan (2 times the maximum cycle time value), then an error is triggered
that causes a transition to STOP mode.
In STOP mode, your program execution stops while CPU system communications and
system diagnostics continue.
262
Description
RE_TRIGR (Re-trigger scan time watchdog) is used to extend the maximum
time allowed before the scan cycle watchdog timer generates an error.
Minimum value
1 ms
Maximum value
6000 ms
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
Default value
150 ms