Expansion module address method and apparatus for a programmable logic controller
First Claim
1. 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.
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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.
75 Citations
20 Claims
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1. 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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An addressing apparatus for each of a plurality of input/output expansion modules having the same predetermined selection address and serially coupled to one another and coupled with a programmable logic controller, comprising:
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an address line for receiving a predetermined address identifier into one of the expansion modules and transmitting a modified said predetermined address identifier to another address line of another one of the expansion modules; and
,address control logic coupled to said address line for selecting said one of the expansion modules when the received predetermined address identifier equates with said predetermined selection address and decrementing the received predetermined address identifier by one incremental address position for transmission to another one of the expansion modules subsequently coupled from said one of the expansion modules when the received predetermined address identifier does not equate with said predetermined selection address, said programmable logic controller being configured with the incrementing address positions of each of the expansion modules and transmitting said predetermined address identifier to one of the expansion modules serially coupled first from said programmable logic controller. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification