Browse Prior Art Database

Time Shared Device Controller Interface

IP.com Disclosure Number: IPCOM000076249D
Original Publication Date: 1972-Feb-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Cummings, JC: AUTHOR [+5]

Abstract

Interface between an I/O controller (CU) and a controlled device, such as a magnetic tape unit (MTU), uses an architecture similar to the IBM System 360 I/O Channel. Bus in, bus out, and tag lines are provided. One of the tag lines from MTU to CU is TACH/busy-not busy. Multiplexing the one tag line between busy-not busy when MTU is not operating and for capstan-motor tachometer pulses when operating under CU direction, reduces the number of lines in the interface.

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Time Shared Device Controller Interface

Interface between an I/O controller (CU) and a controlled device, such as a magnetic tape unit (MTU), uses an architecture similar to the IBM System 360 I/O Channel. Bus in, bus out, and tag lines are provided. One of the tag lines from MTU to CU is TACH/busy-not busy. Multiplexing the one tag line between busy-not busy when MTU is not operating and for capstan-motor tachometer pulses when operating under CU direction, reduces the number of lines in the interface.

Gating means in MTU selectively supply the multiplexed signals over the one tag line. In one arrangement, if there are no other tags being sent from MTU to CU, the busy-not busy signal is supplied. If, however, any tag line is activated, then the tachometer pulses are supplied.

In another version, the busy-not busy signal is supplied except when certain commands are issued by CU to MTU, whereupon tachometer pulses are supplied only during execution of such commands.

In summary, the one tag line during initial selection indicates whether or not MTU is busy. Also, when there is a multiplexing switch between one or more CU's and a plurality of MTU's, it indicates whether or not the switch lines to a given MTU are busy. This one tag line also transfers information that the MTU is busy during an independent operation, indicates response to an independent operational command from CU, also indicates termination of an independent operation, and tachometer performance. In...