# US 2008/0189492 A1 · System, method and storage medium for controlling asynchronous updates to a register

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- Number: US 2008/0189492 A1
- Document ID: US20080189492A1
- Status: Published application
- Kind: A1
- Application number: 12/105,816
- Filed: 2008-04-18
- Published: 2008-08-07
- Earliest claimed: 2004-04-08
- Assignees: International Business Machines Corporation
- Inventors: Michael Billeci
- Web page: https://patentgrep.com/patent/US20080189492A1

## CPC

- G06F 9/30098: {Register arrangements}
- G06F 9/52: Program synchronisation; Mutual exclusion, e.g. by means of semaphores
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

A system for controlling asynchronous updates to a register, the system including a generally accessible register that is asynchronously updateable by hardware and software. The system also includes protection logic that is in communication with the register. The protection logic includes circuitry to prevent a hardware update to the register from being overwritten by a software update.

## Claims

### Claim 1

A computer program product for controlling asynchronous updates to a register, the computer program product comprising:
a storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising:
processing a software read instruction for a bit within the register, the software read instruction a read portion of a read-modify-write instruction;
storing the value of the bit read by the software read instruction in a last read field;
receiving a software write request to the bit, the software write request a write portion of the read-modify-write instruction;
comparing a current value of the bit to the last read field; and
preventing processing of the software write request if the current value of the bit is not equal to the last read field.