The PLC processor contains several areas of memory.
The program memory is where the program instructions are stored. Values of I/O points and internal memory, such as bit values, integer values, floating-point values, timers, and counters are organized in Data Files, separated by type of data.
The Micrologix 1100 has the capacity for 4 kilo-words of program memory and 4 kilo-words of data table memory. This is enough for a program memory for about 50 medium-complexity rungs and enough data table space to support 500 bits, 250 integers, 100 real number values, and 50 timers and counters, with plenty of memory left over for future logic additions.
There are two data files, O0, which stores values from digital output cards, and I1, which stores values from digital output cards.
The addresses within each data file are set by the I/O rack and module in which the I/O card resides.
The MicroLogix 1100 comes with 10 digital inputs, 2 analog inp...
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 orde...
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 ...
