Browse Prior Art Database

Automatic I/O Switching

IP.com Disclosure Number: IPCOM000096892D
Original Publication Date: 1962-Jan-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Cullen, JW: AUTHOR [+2]

Abstract

The circuit switches, under program control, an I/O unit, such as a tape unit, either between two channels of the same computer or between the channels of different computers.

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Automatic I/O Switching

The circuit switches, under program control, an I/O unit, such as a tape unit, either between two channels of the same computer or between the channels of different computers.

To operate the circuit, three types of inputs are needed which are brought up by the instructions:
1. Disconnect -- channel address -- unit address. This is a disconnect instruction which switches the I/O unit specified by the unit address, from an on line status to a stand by status, in which it is not connected to either channel but is available to either channel. This instruction actuates line 1 or 4 according to which channel is to be disconnected from the I/O unit.
2. Test channel address -- unit address. This instruction tests the addressed I/O unit to see if it is connected to the addressed channel or is in stand by status. This instruction actuates line 3 or 6 according to which channel is to be tested for a connection to the I/O unit. If the I/O unit is not connected to the addressed channel or is in stand by status, line 8 or 10 is actuated to tell the program to proceed with other matters.
3. Select -- channel address -- unit address. This instruction actuates line 2 or 4 according to which channel is addressed and brings up output 7 or 9, respectively, which causes the I/O unit to be connected to the addressed channel.

When power is brought up on the I/O unit, it is placed in stand-by status, in which it is not connected to either channel A or
B. if compu...