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Browse Prior Art Database

Circuit to Provide Asynchronous Access to a Common Register Set

IP.com Disclosure Number: IPCOM000036848D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Bailey, RN: AUTHOR [+3]

Abstract

Disclosed is a mechanism which provides three independently operating circuits access to a common register set.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 67% of the total text.

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Circuit to Provide Asynchronous Access to a Common Register Set

Disclosed is a mechanism which provides three independently operating circuits access to a common register set.

A block diagram of the overall circuit is shown above. A multi- port register file, having two write ports and three read ports, serves as the common register set. The write controls and data inputs on write port 1, along with the read controls on read ports 1 and 2, are multiplexed between the asynchronous circuits which need access to the register set. The register file controller manages this access by tracking the state of the master controller and makes the appropriate connections.

In the active state, the register file controller connects the receive circuit to write port 1 of the register file. This is accomplished by switching the data in, address and write enable signals for write port 1 to the receive circuit. In addition, the system DMA circuit is connected to read port 1, and the transmit circuit is connected to read port 2. This set of connections allows the receive and transmit circuits to instantly access the appropriate registers without arbitration overhead. Also, the DMA circuit can independently access the tag table information stored in the register file, to transfer the received data back to main storage.

In the inactive state, write ports 0 and 1 and read ports 0 and 1 are connected to the system interface. This allows the system to have instant access to the entire se...