Browse Prior Art Database

Remote LSSD Scan Ring Control

IP.com Disclosure Number: IPCOM000035304D
Original Publication Date: 1989-Jul-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Fuhs, RE: AUTHOR [+2]

Abstract

On past processor designs, the level-sensitive scan design (LSSD) scan rings have been used for hardware debug, software debug, and for processor initialization at IPL. These functions are collectively called the service functions.

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Remote LSSD Scan Ring Control

On past processor designs, the level-sensitive scan design (LSSD) scan rings have been used for hardware debug, software debug, and for processor initialization at IPL. These functions are collectively called the service functions.

In the figure, an existing device on the I/O bus is used for software control of the processor's scan rings. A special service adapter is not required for the processor service functions. The operating system on the existing device provides a higher level programming interface than would be obtainable through a special adapter like those which have been used in the past.

Using this design, messages or packets of scan ring information are passed across the normal I/O bus to the processor rather than through a specially designed adapter.

The processor's I/O bus interface hardware decodes these messages and performs atomic units of a service function on all the other parts of the processor.

Normal bus I/O interface hardware with some minor modifications and additional features can be used to perform all the LSSD scan ring operations required to perform the service functions.

The control of the service functions resides in the software of the existing device of the I/O bus.

With this design, special service messages are sent from the existing device to the processor across the normal I/O bus to do scan ring operations. The processor I/O bus interface hardware decodes or reads these messages. This decoded infor...