Browse Prior Art Database

Process to Release and Reuse Time Slots in a Loop Communications System

IP.com Disclosure Number: IPCOM000077242D
Original Publication Date: 1972-Jun-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Dixon, RC: AUTHOR [+4]

Abstract

Referring to Fig. 1, there is shown a loop communications system having a plurality of n terminals 5, 17, 31 serially coupling a transmission control unit 1 over a two-wire loop transmission Path 3. The control unit impresses synchronous formatted messages of equal and fixed length among n time slots. The format of each message includes an address portion designating the terminal to which the message is intended, a data portion, and a synchronization and block check portion. Each terminal comprises a delay element (11, 23, 33) for temporarily storing each message for at least a portion of the time slot as the message propagates through the loop. As the address portion is the first portion of any message to enter into the delay element, it conveniently can be decoded by decode logic (9, 21, 37).

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Process to Release and Reuse Time Slots in a Loop Communications System

Referring to Fig. 1, there is shown a loop communications system having a plurality of n terminals 5, 17, 31 serially coupling a transmission control unit 1 over a two-wire loop transmission Path 3. The control unit impresses synchronous formatted messages of equal and fixed length among n time slots. The format of each message includes an address portion designating the terminal to which the message is intended, a data portion, and a synchronization and block check portion. Each terminal comprises a delay element (11, 23, 33) for temporarily storing each message for at least a portion of the time slot as the message propagates through the loop. As the address portion is the first portion of any message to enter into the delay element, it conveniently can be decoded by decode logic (9, 21, 37). The decode logic operatively controls a corresponding transmit switch (S1, S2, Sn). Each transmit switch normally connects its associated delay element to the loop (S1-13, S2-25, Sn-43). When the decode logic decoded either its own terminal address or a special character and it desires to seize the slot such as by inserting its own message, then the transmit switch is activated and connects the message transmitter (14, 26, 38) to the loop through an appropriate contact closure (15, 27, 41). The terminal transmitter is, of course, connected only for the duration of the time slot. The slot is seized either for the purpose of the terminal transmitting a message to another address or for the terminal to, in effect, write over the address portio...