US 5,802,389 A · Expansion module address method and apparatus for a programmable logic controller

Abstract

An expansion module address method and apparatus for a Programmable Logic Controller (PLC) is taught. Briefly stated, a PLC base unit sends an address to an expansion module or modules attached thereto. Each expansion module takes the address number it receives and considers it to be its own address number. Unless the number presented to it is a zero, the expansion module decrements the number and passes it onto the next module. Thereby each module knows its own address. Each expansion module has contained therein a plurality of address and data lines which are common to all modules with the exception of one address line which is interrupted by each module circuitry, which is used to decrement the address number and then passes it along the interrupted address line to the next module.

Claims20

Dependent claims

A method of addressing a plurality of expansion modules serially coupled to one another when coupled to a programmable logic controller (PLC), comprising the steps of:

transmitting a predetermined address identifier to one of the expansion modules coupled first from said PLC, each of the expansion modules having the same internal address for being selected, said PLC being configured with the location of each of the expansion modules;
responding by said one of the expansion modules as being selected when said predetermined address identifier received equates with said internal address;
decrementing said predetermined address identifier by one address position, by said one of the expansion modules, when said predetermined address received does not equate with said internal address;
transmitting the decremented predetermined address identifier to another one of the expansion modules subsequently coupled from said one of the expansion modules;
and,
repeating the steps of decrementing and transmitting said predetermined address identifier from said another one of the expansion modules to the remaining expansion modules until one of the expansion modules is selected when the decremented predetermined address identifier equates with said internal address.

3 more elements

Dependencies are inferred from the claim text.

Expansion module address method and apparatus for a programmable logic controller

Life of this patent

Expansion module address method and apparatus for a programmable logic controller

Life of this patent

Abstract

Claims20