Example Code For Query Semaphore - Analog Devices Blackfin ADSP-BF537 Hardware Reference Manual

Hide thumbs Also See for Blackfin ADSP-BF537:

Table of Contents

Semaphore coherency is guaranteed by using the test and set byte (atomic)

instruction (

• Loads the half word at memory location pointed to by a P-register.

The P-register must be aligned on a half-word boundary.

• Stores the value back in its original location (but with the most sig-

nificant bit (MSB) of the low byte set to 1).

The events triggered by

memory where the address is located is acquired and not relinquished

until the store operation completes. In multithreaded systems, the

instruction is required to maintain semaphore consistency.

To ensure that the store operation is flushed through any store or write

buffers, issue an

instruction can be used to implement binary semaphores or

any other type of mutual exclusion method. The

ports a system-level requirement for a multicycle bus lock mechanism.

The processor restricts use of the

ory region only. Use of the

of the memory map may result in unreliable behavior.

Example Code for Query Semaphore

Listing 21-1

provides an example of a query semaphore that checks the

availability of a shared resource.

ADSP-BF537 Blackfin Processor Hardware Reference

if the value is equal to zero.

instruction immediately after semaphore release.

instruction performs these functions.

are atomic operations. The bus for the

instruction to the external mem-

instruction to address any other area

System Design

instruction sup-