Chapter 4. Ladder Diagram (LD) Programming202 PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual GFK-2950C4.11.1 Argument PresentThe ARG_PRES function determines whether an input parametervalue was present when the function block instance of theparameter was invoked. This may be necessary if the parameter isoptional.This function must be called from a function block instance or aparameterized block.The standard output parameter ENO is false only when EN is false.Operands for ARG_PRESParameter Description Allowed Operands OptionalIN Parameter name. Must be a parameter of the functionblock that contains the ARG_PRES instruction. Cannotbe an array element or structure element. An alias toa parameter should resolve only to the parametername.All except flow and constants. NoQ True if the parameter is present, otherwise false. Must be flow in LD. In otherlanguages all types allowedexcept S, SA, SB, SC andconstants.NoExample for ARG_PRESThe following sample rung calls the user defined function block, ReadTemp, which has twoparameters, TempVal and Temp1.The function block ReadTemp contains the following logic, which uses an ARG_PRES function todetermine whether a value for TempVal is present. If TempVal does not have a value, Temp_Pres isOFF and Idle is ON. If a value exists for TempVal, the ARG_PRES function sets Temp_Pres ON. WhenTemp_Pres and Switch are both ON, Start is set ON.
