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Topographical Addressing on Loops

IP.com Disclosure Number: IPCOM000077265D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 3 page(s) / 49K

Publishing Venue

IBM

Related People

Widmer, AX: AUTHOR

Abstract

Information about the sequential order of devices in a loop is stored. All devices are designed to manipulate certain bits of frames of data supplied by the loop following uniform rules. Each device has an adaptor designed to accept the "identical address" data as its own address, because each device transforms the bits in accordance with the rules to ultimately provide that "identical address".

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Topographical Addressing on Loops

Information about the sequential order of devices in a loop is stored. All devices are designed to manipulate certain bits of frames of data supplied by the loop following uniform rules. Each device has an adaptor designed to accept the "identical address" data as its own address, because each device transforms the bits in accordance with the rules to ultimately provide that "identical address".

In a loop communication system, a selected terminal is addressed by its topological position in the loop. A controller has a stored table of connected terminals and their relative, sequential positions in the loop. The controller enters an address on the loop representing the count of any selected one of the sequential positions. Each of a plurality of connected terminals has identical means for changing that address by a fixed increment, comparing the changed address with a stored reference value, and accepting message frames whose changed addresses compare equal to the stored reference value.

In Fig. 1, a loop controller 10 is provided which sends out frames of data sequentially, as shown in Fig. 2, with the first portion of each frame comprising the status bits (S) indicating by a 1 bit that the frame is full and by a 0 bit that the frame is empty. The next segment contains the address bits which contain the address code to determine which communications adaptor 11. 12, or 13 is to accept the data (D) contained within the frame. Each communications adaptor responds to the "identical address" which for a two-bit binary address system will be assumed to be binary 00. At point 14. three frames are shown entering adaptor 11, including S/00/D, S/01/D, and S/10/D. The first frame will be accepted by adaptor 11 and its data (D) is passed to device 15, and its address decremented by one to S/11/D at point 16. Frame 2 address is decremented from S01D to S00D so that it is accepted by adaptor 12. Frame 3 address is decremented by adaptor 11 from S/11/D to S/01/D and adaptor 12 decrements it to S/00/D so data in frame 3 is accepted by adaptor 12. With more adaptors on the loop, the address bits are greater in number. When controller 10 addresses adaptor 13, it places binary number 10 (i.e. decimal two) in the frame address. Controller 10 checks the ret...