Browse Prior Art Database

Alteration of ROS Resident Programs

IP.com Disclosure Number: IPCOM000087030D
Original Publication Date: 1976-Dec-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Crandall, DR: AUTHOR [+2]

Abstract

In microprogrammed devices, the control program is usually built in and will be embodied in a read-only store (ROS). Such machines also may have a small section of a random-access memory which can be set and reset. It is expensive and time consuming to make changes in the ROS program by generating a new ROS for each error correction, introduction of new functions or other engineering changes. The system described herein can be used to modify a ROS program until a final ROS version can be procured.

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Alteration of ROS Resident Programs

In microprogrammed devices, the control program is usually built in and will be embodied in a read-only store (ROS). Such machines also may have a small section of a random-access memory which can be set and reset. It is expensive and time consuming to make changes in the ROS program by generating a new ROS for each error correction, introduction of new functions or other engineering changes. The system described herein can be used to modify a ROS program until a final ROS version can be procured.

In such a programmed system, the program code in ROS will have branch instructions scattered through it at key points with the branch to be taken if a selected bit has been set in the random-access memory. The random-access memory will have a settable bit for each of such branch instructions and the associated bit will be tested for each of the branch instructions. In use, when the ROS program is to be altered, the altered program from the last preceding ROS branch point to the end of the corrections will be entered into random-access memory and the bit corresponding to the branch will be set. Then, when the program progresses to the branch point and tests the set bit, the branch is taken into the random-access memory program which is executed until the end of the patch where a last instruction returns execution of the program back into the ROS instructions.

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