Browse Prior Art Database

Transparent Buffered Control Unit

IP.com Disclosure Number: IPCOM000092163D
Original Publication Date: 1968-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Brown, DT: AUTHOR

Abstract

A seek command is utilized in direct access storage devices, such as disks, to cause the access mechanism to move to the required position. If a command code is decoded as a seek operation, the control unit first selects the disk drive module. The selected module indicates to the control unit the present location of its access mechanism. This present location is known as the old address. The control unit uses the old address and a seek address received from the channel to calculate the direction and number of cylinders or tracks the access mechanism must move. This control information is then sent to the disk module. Circuits in the module cause the access mechanism and the associated read-write heads to move to the desired cylinder or track.

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Transparent Buffered Control Unit

A seek command is utilized in direct access storage devices, such as disks, to cause the access mechanism to move to the required position. If a command code is decoded as a seek operation, the control unit first selects the disk drive module. The selected module indicates to the control unit the present location of its access mechanism. This present location is known as the old address.

The control unit uses the old address and a seek address received from the channel to calculate the direction and number of cylinders or tracks the access mechanism must move. This control information is then sent to the disk module. Circuits in the module cause the access mechanism and the associated read-write heads to move to the desired cylinder or track. The module then indicates to the control unit that it has completed the seek and the control unit indicates to the channel that the operation is complete by issuing a device end signal.

Once the seek operation is completed, other commands such as read, write, or search can be executed. During a search command, the channel operates in write mode and the disk control unit operates in read mode. The control unit compares the information coming from CPU main storage via the channel with information read from the module. If the search specified by the command is satisfied, a status modifier indication occurs and the channel goes on to the next command. Each time the search is unsuccessful, the channe...