Semaphores
19-6
ADSP-BF535 Blackfin Processor Hardware Reference
The ADSP-BF535 processor supports nested and non-nested interrupts,
as well as self-nested interrupts. For explanations of the various modes of
servicing events, see
“Interrupts With and Without Nesting” on
page 4-48
.
Semaphores
Semaphores provide a mechanism for communication between multiple
processors or processes/threads running in the same system. They are used
to coordinate resource sharing. For instance, if a process is using a particu-
lar resource and another process requires that same resource, it must wait
until the first process signals that it is no longer using the resource. This
signaling is accomplished via semaphores.
Semaphore coherency is guaranteed by using the Test and Set Byte
(Atomic) instruction (
TESTSET
). The
TESTSET
instruction performs these
functions.
• Loads the byte at memory location pointed to by a P-register.
• Sets
CC
if the value is equal to zero.
• Stores the value back in its original location (but with the most sig-
nificant bit set to 1).
The events triggered by
TESTSET
are atomic operations. The bus for the
memory where the address is located is acquired and not relinquished
until the store operation completes. In multithreaded systems, the
TESTSET
instruction is required to maintain semaphore consistency.
To ensure that the store operation is flushed through any store or write
buffers, issue an
SSYNC
immediately after semaphore release.
Summary of Contents for ADSP-BF535 Blackfin
Page 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Page 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Page 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Page 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Page 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Page 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Page 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Page 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Page 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...