There are two special files, called forcing files, one for inputs and one for outputs.
These files are used for troubleshooting or when I/O is not available, such as when a sensor fails.
The forcing files allow the value supplied by the I/O subsystem to be over-written by the programmer in order to compensate for lost or incorrect values due to sensor loss or malfunction.
In the last lesson, we briefly described the data files. Now, we will describe these files in more depth and show how they are used.
Note that each data file is described by a letter followed by a number.
The letter indicates the type of data represented by that file, and the number represents ...
Output file 0 and Input file 1 are defined to hold values from physical I/O cards.
All of the data files are presented in much the same way. The Output file holds values that are associated with physical output cards. For a MicroLogix 1100, up to 64 outputs, or four 16-bit output words, can be ...
The structure of the Input file is the same as the Output file.
File I1 represents the physical input device addresses possible.
Notice that there are six 16-bit input words available, representing the possible 96 inputs for the PLC.
In a later lesson, we will add descriptions and symbols f...
