Browse Prior Art Database

Remote Unit Busy Indicator

IP.com Disclosure Number: IPCOM000092100D
Original Publication Date: 1968-Sep-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Palounek, LR: AUTHOR [+2]

Abstract

The apparatus prevents a central system from selecting a remote unit which is busy or which is about to be busy but has not had sufficient time to communicate back to the system that it has been selected and is to be busy. Remote unit RU is selected by the Select Remote Unit line connected through the normally nonactivated Inhibit to RU via line 2. When RU receives a select signal over line 2, it sends back a busy signal over line 3. This signal sets the Busy Trigger causing it to have a Busy output. Such output energizes through Or 2 the Inhibit thus preventing any further selection of the RU while it is in the Busy condition.

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Remote Unit Busy Indicator

The apparatus prevents a central system from selecting a remote unit which is busy or which is about to be busy but has not had sufficient time to communicate back to the system that it has been selected and is to be busy. Remote unit RU is selected by the Select Remote Unit line connected through the normally nonactivated Inhibit to RU via line 2. When RU receives a select signal over line 2, it sends back a busy signal over line 3. This signal sets the Busy Trigger causing it to have a Busy output. Such output energizes through Or 2 the Inhibit thus preventing any further selection of the RU while it is in the Busy condition.

The relatively long time delay required in communicating with RU over lines 2 and 3 is a problem because of the speed at which the system, and thus the Select Remote Unit line, operates. Since the Select Remote Unit line operates at speeds in the nanosecond range or faster, that line can attempt to select RU several times before a Busy signal, responsive to the first selection, returns over line 3. In order to prohibit more than one selection of RU at one time, the first signal on the Select Remote Unit appearing on line 2 is supplied to the first stage A of counting chain 4.

With an input to stage A, chain 4 is stepped, by the clock input, from stage A through stage G and the outputs B...F are combined in Or 1 to develop a Pseudo Busy signal. This energizes through Or 2 the Inhibit to prevent any further selecti...