Figure 3-20 shows the POR sequence of the MPU subsystem.
The assumptions after power-on reset assertion are:
- The PRCM module provides the DPLL_MPU reference clock and the bypass clock.
- The PRCM module has released DPLL_MPU reset and DPLL_MPU is in bypass mode providing the clock (that is, bypass clock) to all the modules in the MPU subsystem.
The POR sequence is:
- The PRCM module releases asynchronously in PD_MPUAON the MPUAON_RST reset to the INTC_MPU module in the MPU subsystem.
- The PRCM module releases in PD_MPU the MPU_PWRON_RST (only after MPU_DPLL_CLK is active) to the MPU subsystem and waits until the subsystem completes its internal reset sequence. MA_MPU (Memory-adapter) dedicated reset signals (MPU_MA_RST, MPU_MA_RET_RST, and MPU_MA_PWRON_RET_RST) are released when MPU_DPLL_CLK is running (at the same time as MPU_PWRON_RST). When PRCM receive active MPU_RSTDONE signal from MPU, it de-asserts MPU_RST.
- When the MPU subsystem internal reset sequence completes, the PRCM module releases in PD_MPU the MPU_RST signal and the MPU starts booting.
- The PRCM module drives the MPU_L2RSTDISABLE signal low a minimum of 32 SYS_CLK cycles after MPU_RST is deasserted. The PRCM module keeps the MPU_L2RSTDISABLE signal low until the next power domain transition.
Note: - The reset to the L2 cache memory (MPU_L2RSTDISABLE) in the MPU subsystem is asserted during initial POR (that is, when the PD_MPU wakes up from OFF state). It is also asserted during local or global warm reset. However, it is not asserted when the PD_MPU wakes up from RETENTION state (that is, when the logic is OFF and L2 memory is in RETENTION state). This ensures that the L2 cache is retained on wakeup.
- The L1 cache memory in the MPU subsystem is not retained on PD_MPU wakeup.