FB_WriteWatchdog

Writing a watchdog signal to another ADS device (TwinCAT PLC, Bus Terminal Controller, ...).

The FB_WriteWatchdog() function block cyclically writes the contents of a 32-bit counter into another ADS device. The counter is incremented every time the transmission is successful. The FB_CheckWatchdog() function block can be used at the receiver to evaluate this signal. The receiver is addressed by means of the AMS-NetId and the port number (see also ADS Device Identification). The position within the receiver is specified by the index group/index offset or by the symbol name. Usually this is the input image or the flags area.

The period for tWachtdogTime should not be shorter than 1 second, to avoid transmitting the counter state too frequently. If 0 seconds is given for tWatchdogTime, the signal is not transmitted. Please also note the description of the FB_CheckWatchdog() block. If the bEnable input is set to FALSE, no further transmission of the watchdog signal is carried out.

bEnable       : BOOL := FALSE;
sNetId        : T_AmsNetId;
nPort         : T_AmsPort := AMSPORT_R0_PLC_RTS1;
nIdxGrp       : UDINT;
nIdxOffs      : UDINT;
sVarName      : STRING;
tWatchdogTime : TIME := t#0s;
bSendNow      : BOOL;

bBusy        : BOOL;
nLastCnt     : UDINT;
bError       : BOOL;
nErrorId     : UDINT;