Нужно было делать так:
Код:
RTRIG_fbMbRolDone(CLK := fbModbusRol.xDone);

IF RTRIG_fbMbRolDone.Q THEN
	xSuccess := TRUE;
	fbModbusRol.xExecute := FALSE;
	xRdPosReg := FALSE;
END_IF

IF xRdPosReg THEN
	//xSuccess := FALSE;
	wIntPosPOld := GVL.stServo[1].stRdServo.wP700_IntPosP;
	GVL.stServo[1].stWrServo.wP700_IntPosP := 4610;
	GVL.stServo[1].stWrServo.wP765_IntPosDZT := 1000;
	fbModbusRol(slave := ROL_DORNA, xExecute := xExecModbus, iChannelIndex := iCurrentCh);
	ltTimeOfStart := TargetVars.stRtc.ltSystemTick;
	//xRdPosReg := FALSE;
	xCount := TRUE;
	iCntr := iCntr + 1;
END_IF