MPU_CLK
MPU
clock
generator
PRCM
ARM Cortex-A8
Emulation/
trace/debug
I2ASYNC_FCLK (ARM_FCLK/2)
EMU
DPLL
ICECrusher
I2Async
AXI2OCP
INTC
MPU subsystem
AXI2OP_FCLK (ARM_FCLK/2)
INTC_FCLK (ARM_FCLK/2)
ICECRUSHER_FCLK (ARM_FCLK/2)
ARM_FCLK
EMU_CLOCKS
ARM Cortex-A8 MPU Subsystem
All major modules inside the MPU subsystem are clocked at half the frequency of the ARM core. The
divider of the output clock can be programmed with the
PRCM.CM_CLKSEL2_PLL_MPU[4:0]MPU_DPLL_CLKOUT_DIV register field, the frequency is relative to
the ARM core. For details see the Power, Reset, and Clock Management (PRCM) chapter.
The clock generator generates the following functional clocks:
ARM (ARM_FCLK): This is the core clock. It is the base fast clock that is routed internally to the ARM
logic and internal RAMs, including NEON, L2 cache, the ETM core (emulation), and the ARM core.
AXI2OCP Clock (AXI_FCLK): This clock is half the frequency of the ARM clock (ARM_FCLK). The OCP
interface thus performs at one half the frequency of ARM.
Interrupt Controller Functional Clock (MPU_INTC_FCLK): This clock, which is part of the INTC
module, is half the frequency of the ARM clock (ARM_FCLK).
ICE-Crusher Functional Clock (ICECRUSHER_FCLK): ICE-Crusher clocking operates on the APB
interface, using the ARM core clocking. This clock is half the frequency of the ARM clock (ARM_FCLK).
I2Async Clock (I2ASYNC_FCLK): This clock is half the frequency of the ARM clock (ARM_FCLK). It
matches the OCP interface of the AXI2OCP bridge.
NOTE:
The second half of the asynchronous bridge (T2ASYNC) is clocked directly by the PRCM
with the core clock. T2ASYNC is not part of the MPU subsystem.
Emulation Clocking: Emulation clocks are distributed by the PRCM module and are asynchronous to the
ARM core clock (ARM_FCLK) and can run at a maximum of 1/3 the ARM core clock.
Table
summarizes the clocks generated in the MPU subsystem by the MPU clock generator.
Figure 3-3. MPU Subsystem Clocking Scheme
Table 3-1. MPU Subsystem Clock Frequencies
Clock signal
Frequency
Cortex A8 Core Functional Clock
MPU_CLK
AXI2OCP Bridge Functional Clock
MPU_CLK / 2
Device Clock
MPU_CLK / 2
I2Async Bridge Functional Clock
MPU_CLK / 2
168 ARM MPU Subsystem
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated