SPRUHM8K December 2013 – May 2024 TMS320F28374D , TMS320F28375D , TMS320F28376D , TMS320F28377D , TMS320F28377D-EP , TMS320F28377D-Q1 , TMS320F28378D , TMS320F28379D , TMS320F28379D-Q1
Both CPUs can access the PLL and peripheral clock configuration registers. The clock configuration semaphore allows one CPU to access the registers without being interrupted by the other CPU.
The clock configuration semaphore is implemented as a two-bit field in a register with special write protections. This register requires a key field to be written at the same time as the semaphore bits. The possible semaphore states are:
00 or 11 | Either CPU can write to the semaphore. CPU1 has control of the clock configuration registers by default. 00 is the reset state. |
01 | CPU2 has exclusive control of the clock configuration registers and exclusive write access to the semaphore. |
10 | CPU1 has exclusive control of the clock configuration registers and exclusive write access to the semaphore. |
Each CPU is only allowed to take control of the clock configuration registers for itself. However, CPU1 can force both semaphores into the default state (00) at any time by putting CPU2 into reset. Figure 3-21 shows the allowed states and state transitions.