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Browse Prior Art Database

Multistorage Control Interface Switch

IP.com Disclosure Number: IPCOM000080315D
Original Publication Date: 1973-Nov-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 27K

Publishing Venue

IBM

Related People

Luiz, FA: AUTHOR [+2]

Abstract

The switch 1 allows the connection of a controller 4 and its attached drives 5 to two independent storage controls 2 and 3 via the control interface.

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Multistorage Control Interface Switch

The switch 1 allows the connection of a controller 4 and its attached drives 5 to two independent storage controls 2 and 3 via the control interface.

The switch 1 may be connected to one interface and busy to the other, or it may be in the neutral state and available to both interfaces for interrupt polling or selection.

In the absence of any busy condition, a storage control 2 or 3 causes the controller 4 to be switched to itself by the normal selection sequence over the control interface. In the case of simultaneous selection attempts by both storage controls 2 and 3, the outcome is resolved by the switch tie-breaker. If a storage control 2 or 3 gets a busy response to its selection attempt, it becomes partially selected and is allowed to perform certain limited operations on its own side of the switch.

The connection between storage control 2 or 3 and controller 4 is either long or short. A short connection is one that exists for status interrogation and/or reset. All other connections are long.

The switch is in the neutral state when it is not switched to either of the two control interfaces. As soon as it switches to an interface via the selection process, the switch immediately goes to the short-connection state. If the connected storage control 2 or 3 now expects to continue with extended operations, it is required to set the long-connection latch in the switch using the tag provided. This puts the switch in the long-connection state. Upon completion of operations, the connection storage control 2 or 3 disconnects by unlocking the switch using the tag provided and dropping selection, whereupon the switch returns to neutral state.

Any drive 5 attached to the controller 4 via the device interface may be assigned for exclusive use b...