GE PACSystems RXi User Manual

Chapter 7. CPU Program Data122 PACSystems* RXi Distributed IO Controller User Manual GFK-2816FRestrictions on the Use of I/O Variables■ Since I/O variables are a form of symbolic variable, the same restrictions that apply toother symbolic variables of the same data type and array bounds apply to I/O variables.■ Only a global variable can become an I/O variable. A local variable cannot become an I/Ovariable.■ You can map only a discrete variable to a discrete terminal.■ You can map only a non-discrete variable to an analog terminal.■ Arrays and UDT variables must fit on the number of terminals in the reference addressnode counting from and including the terminal where you enter the array head or UDTvariable. For example, if you have 32 analog terminals and you have a WORD array of12 elements, you can map it to terminal 21 or any terminal before it (1 through 20).■ You can map a discrete array only to a terminal 8n+1, where n = 0, 1, 2, and so on. The+1 is present because the terminals are numbered beginning with 1. If you map it to aterminal other than 8n+1, an error occurs upon validation.■ An I/O variable cannot be mapped to more than one location in hardware configuration.■ For the DO_IO function block, if an I/O variable is assigned to the ST parameter, then thesame I/O variable must also be assigned to the END parameter, and the entire module isscanned.I/O Variable FormatYou create I/O variables by assigning them on the Terminals tab in Proficy Machine EditionHardware Configuration. The variable structure is created automatically, and uses the format%vdr.s.[z.]g.t, where:v = I (input) or Q (output)d = data type: X (discrete) or W (analog).[z] = subslot number. Always 0 for RXi Controllers.g = segment number. Always 1 for the RXi Ethernet interface; always 2 for the RXi PNC.t = terminal number. One-based, that is, the numbering begins at 1.Supported I/O Variable TypesData TypeMnemonicSupported DataTypes Number of Consecutive Terminals RequiredXBOOL variable 1BOOL array Number of elements in array.BYTE variable 8BYTE array 8n, where n is the number of array elements.WDINT variable 2DINT array Number of elements in array times 2DWORD variable 2DWORD array Number of elements in array times 2INT variable 1INT array Number of elements in arrayLREAL variable 4LREAL array Number of elements in array times 4REAL variable 2REAL array Number of elements in array times 2UINT variable 1UINT array Number of elements in arrayWORD variable 1WORD array Number of elements in array