Switching Procedure
B-2
B.1 Switching Procedure
Perform the following procedure to switch OMAP5910 clock modes:
1) Make sure the DSP clock is enabled.
2) Make sure there are no active transfers on interfaces (EMIFS, EMIFF,
TIPB, IMIF, MPUI, etc.).
3) Make sure there are no active DSP transactions being performed.
4) Disable the MPU D-cache/MMU.
5) Make sure the MPU clock control register (ARM_CKCTL), clock dividers,
and the DPLL_REG have correct contents for the clock mode the system
is being switched to.
a) Switch from SYNC mode to SYNCSCALE mode:
i)
Make sure that the frequency of the traffic controller is always less
than the maximum frequency of the traffic controller.
ii)
Change the clock mode.
iii) Program the clock dividers.
iv) Program DPLL to frequency desired.
b) Switch from SYNCSCALE to SYNC mode:
i)
Program the DPLL to the desired frequency in synchronous
mode.
ii)
Program all clock dividers to be equal.
iii) Change the clock mode to SYNC mode.
6) After the MPU write to the MPU system status register (ARM_SYSST)
(0x18) to switch modes, there must be no requests from the MPU to the
traffic controller for the next 100 MPU cycles (see Section B.2, Main Code,
and Section B.3, Delay Procedure ).
7) Make sure all read and write accesses to the clock reset registers are
16-bit accesses.