6.17 Semaphore2

The device contains an enhanced semaphore module for the management of shared resources of the DSP C66x CorePac. The semaphore enforces atomic accesses to shared chip-level resources so that the read-modify-write sequence is not broken. The semaphore module has a unique interrupt to the CorePac to identify when the core has acquired the resource.

Semaphore resources within the module are not tied to specific hardware resources. It is a software requirement to allocate semaphore resources to the hardware resource(s) to be arbitrated.

The semaphore module supports 8(C6655) or 2(C6657) masters and contains 32 semaphores to be used within the system.

The Semaphore module is accessible only by masters with privilege ID (privID) 0(C6655) or 0 to 1(C6657), which means only CorePac 0 (C6655) or 0 to 1(C6657) or the EDMA transactions initiated by CorePac 0(C6655) or 0 to 1(C6657) can access the Semaphore module.

There are two methods of accessing a semaphore resource:

• Direct Access: A core directly accesses a semaphore resource. If free, the semaphore will be granted. If not, the semaphore is not granted.
• Indirect Access: A core indirectly accesses a semaphore resource by writing it. Once it is free, an interrupt notifies the CPU that it is available.