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Browse Prior Art Database

Loading Microcode Engineering Change Files to Attachment Cards of a Technician's Terminal

IP.com Disclosure Number: IPCOM000039993D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 66K

Publishing Venue

IBM

Related People

Greene, WB: AUTHOR

Abstract

This article describes a technique utilizing check points for patching the code resident in read-only memory (ROM) or erasable programmable ROM (EPROM) and checksumming the engineering change (EC) code for correct loading to attachment cards of a technician's terminal. In the technique disclosed herein in order that the microcode can check if an EC had been loaded, two instructions must be placed in the microcode at points where checking would be desirable. The first instruction places a value in the accumulator and defines the check point to be checked. The second instruction calls a subroutine that does the checking. This reduces the amount of code needed to check each EC patch point. The subroutine uses the number in the accumulator to index into the random-access memory (RAM) and retrieve a number.

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Loading Microcode Engineering Change Files to Attachment Cards of a Technician's Terminal

This article describes a technique utilizing check points for patching the code resident in read-only memory (ROM) or erasable programmable ROM (EPROM) and checksumming the engineering change (EC) code for correct loading to attachment cards of a technician's terminal. In the technique disclosed herein in order that the microcode can check if an EC had been loaded, two instructions must be placed in the microcode at points where checking would be desirable. The first instruction places a value in the accumulator and defines the check point to be checked. The second instruction calls a subroutine that does the checking. This reduces the amount of code needed to check each EC patch point. The subroutine uses the number in the accumulator to index into the random-access memory (RAM) and retrieve a number. If this number is zero, x'00', then no EC has been loaded for this portion of code. If the number be not zero, this indicates that an EC has been loaded and also the displacement to find the first instruction of the EC. The subroutine removes the address of the CALL instruction from the STACK and branches to the first instruction of the code to be changed. Whenever an EC is loaded, it must repeat the code between the check point and the problem that is to be corrected. The correction is then made and the code can branch back to the microcode in the ROM or EPROM to continue the...