Allen-Bradley 1747-L514

The SLC 500 controllers provides status file functions, provides the instructions used in your ladder logic programs and compliments the online help available at the terminal. Basic instructions, when used in ladder programs, represent hardwired logic circuits used for the control of a machine or equipment. The basic instructions are separated into three groups: bit, timer, and counter.

SLC 500 user memory is comprised of Data Files and Program Files. Data Files 0 and 1 represent external outputs and inputs, respectively. Bits in file 1 are used to represent external inputs. In most cases, a single 16-bit word in these files will correspond to a slot location in your controller, with bit numbers corresponding to input or output terminal numbers. Unused bits of the word are not available for use.