F142_WDT

Watchdog timer update

The scan ‘check watchdog timer’ is preset with the constant specified by s if the trigger EN is in the ON-state. The value specified by s* is 1 to 255 and the preset time becomes 2.5 ms * s* (637.5 ms).

Parameters

Input

s* (INT): specifies watchdog timer value

Remarks

Instead of using this F instruction, we recommend using the corresponding FP7 instruction: FP_RESET_WATCHDOG
The scan ‘check watchdog timer’ is automatically set at the start of a scan with the value of the system register (No. 30). To monitor the transit of a processing block, set the watchdog timer with this instruction immediately before transition and set again immediately after that.

Example

POU header

All input and output variables used for programming this function have been declared in the POU header. The same POU header is used for all programming languages.

	VAR
		start: BOOL:=FALSE;
			(*activates the function*)
	END_VAR

POU body

When the variable start is set to TRUE, the function is carried out.

LD body

BODY
    WORKSPACE
        NETWORK_LIST_TYPE := NWTYPELD ;
        ACTIVE_NETWORK := 0 ;
    END_WORKSPACE
    NET_WORK
        NETWORK_TYPE := NWTYPELD ;
        NETWORK_LABEL :=  ;
        NETWORK_TITLE :=  ;
        NETWORK_HEIGHT := 6 ;
        NETWORK_BODY
B(B_F,F142_WDT,,10,0,18,4,,?DEN?H@'s'?AENO);
B(B_VARIN,,1234,8,2,10,4,);
B(B_CONTACT,,start,3,1,5,3,);
L(1,0,1,6);
L(1,2,3,2);
L(5,2,10,2);
        END_NETWORK_BODY
    END_NET_WORK
END_BODY

ST body

IF start then
    (* Watchdog timer value is changed to 123.4ms *)
    F142_WDT(1234);
END_IF;