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CPU 948 Programming Guide
C79000-G8576-C848-04
Before disabling or enabling a particular semaphore, the SED and SEE
operations scan the status of the semaphore. The condition codes CC 0
and CC 1 are affected as follows:
CC 1
CC 0
Evaluation
0
0
1
0
JN, JP
Note
The scanning of a particular semaphore (= read procedure) and
the disabling or enabling of the semaphore (=write procedure) are
one unit. No other CPU can access the semaphore during these
procedures!
When using semaphores, remember the following points:
• • A semaphore is a global variable, i.e. the semaphore with number
16 exists only once in the entire system, even if your controller is
using three CPUs.
• • All CPUs that require coordinated access to a common memory area
must use the SED and SEE operations.
• • All participating CPUs must execute the same start-up type. Du-
ring a COLD RESTART, all the semaphores are cleared. During a
manual or automatic warm restart, the semaphores are retained.
• • Start-up in multiprocessor operation must be synchronized. For
this reason, no test operation is allowed.
Semaphore Operations
Significance
JZ
Semaphore was disabled by
another CPU and cannot be
disabled/enabled.
Semaphore was disabled/
enabled.
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