Browse Prior Art Database

Read Only Store Patch

IP.com Disclosure Number: IPCOM000052373D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Doehle, L: AUTHOR [+3]

Abstract

In a modular read-only store (ROS) configuration, as shown in Fig. 1, all ROS information is accessed via a branch vector table (BVT). This BVT contains the addresses of all entries to the ROS information, such as micro-code routines. In the illustrated configuration, ROS module A contains the BVT and part of the micro-code.

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Read Only Store Patch

In a modular read-only store (ROS) configuration, as shown in Fig. 1, all ROS information is accessed via a branch vector table (BVT). This BVT contains the addresses of all entries to the ROS information, such as micro-code routines. In the illustrated configuration, ROS module A contains the BVT and part of the micro-code.

For easy and inexpensive micro-code changes, the empty EPROM (electrically programmable read-only memory) socket is used to accommodate an erasable programmable ROS (EPROM) which contains a new BVT and the changed micro-code (Fig. 2).

The new BVT replaces the old one by deactivating the latter. As all micro- code accesses to the ROS modules are subsequently controlled by the new BVT, the new parts of the changed micro-code are read straight from the EPROM.

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