FB_WriteWatchdog

Writing of 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 s is given for tWatchdogTime, the signal is not transmitted. Please also note the description of the function block FB_CheckWatchdog ().

If the input bEnable is set to FALSE, no further transfer of the watchdog signal takes place.

VAR_INPUT

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

bEnable: Enable function block.

sNetId: AMS NetID of the ADS device to which the watchdog signal is to be transferred. (Type T_AmsNetId)

nPort: AMS port number of the ADS device to which the watchdog signal is to be transferred. (Type T_AmsPort)

nIdxGrp: Index group within the ADS device to which the watchdog signal is to be transferred.

nIdxOffs: Index offset within the ADS device to which the watchdog signal is to be transferred.

sVarName: Symbol name within the ADS device to which the watchdog signal is to be transferred.

tWatchdogTime: Cycle time in which the watchdog signal is transferred.

bSendNow: A positive edge triggers immediate transfer of the watchdog signal.

VAR_OUTPUT

VAR_OUTPUT
    bBusy     :  BOOL := FALSE;
    nLastCnt  :  UDINT := 0;
    bError    :  BOOL := FALSE;
    nErrorId  :  UDINT := 0;
END_VAR

bBusy: Transmission is active.

nLastCnt: Most recently transmitted counter state.

bError: An error occurred during the transmission.

nErrorId: Error number if an error has occurred.

Requirements

Development environment	required TC3 PLC library
TwinCAT v3.0.0	Tc2_DataExchange