Browse Prior Art Database

Line Scanner Providing Priority Controls

IP.com Disclosure Number: IPCOM000074128D
Original Publication Date: 1971-Mar-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Barker, WA: AUTHOR [+3]

Abstract

In data multiplexing units, it is desirable to be able to scan all attached lines for service requests and to service such lines with the appropriate priorities. The line scanner mechanism shown will fulfill the usual scanning requirements and requires a minimum amount of hardware, plus it provides the flexibility to assign and/or change priorities to lines without regard to physical line positioning.

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Line Scanner Providing Priority Controls

In data multiplexing units, it is desirable to be able to scan all attached lines for service requests and to service such lines with the appropriate priorities. The line scanner mechanism shown will fulfill the usual scanning requirements and requires a minimum amount of hardware, plus it provides the flexibility to assign and/or change priorities to lines without regard to physical line positioning.

The priority circuits are for a plurality of line adapters 1, one for each transmission line 2 and are connected to the adapters 1 by a wire cable 3. Cable 3 contains among other wires, a set of address lines 4 and a common service request line 5. When the address of a line adapter 1 is placed on lines 4, the line adapter 1 will put a signal on line 5 if service is needed. The line adapters are sequentially addressed by an address counter 7 which is incremented by signals on a line 8 and is reset by a signal on line 9. A small priority counter 6 is incremented by a signal on line 10 each time counter 7 is incremented from its highest reading to zero and is also reset by line 9. Line 9 is energized by either a program controlled reset signal on line 11 or by a machine reset signal on line 12, the two signals being combined in an OR circuit 13.

To accommodate the service requests from line adapters 1 in order of their priority, the line address on lines 4 is decoded to address storage 14 containing a priority table to enter int...