Texas Instruments TMS320C6454 - Manual (Page 54)

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Reset
Static
Powerdown
Disabled
Enable In
Progress
Enabled
Unlock the PERCFG0 register by
using the PERLOCK register.
Write to the PERCFG0 register
within 16 SYSCLK3 clock cycles
to change the state of the
peripherals.
Poll the PERSTAT registers to
verify state change.
TMS320C6454
Fixed-Point Digital Signal Processor
SPRS311A – APRIL 2006 – REVISED DECEMBER 2006
Following device reset, all peripherals that are not in the static powerdown state are in the disabled state
by default. Peripherals used for boot such as HPI and PCI are enabled automatically following a device
reset.
Peripherals are only allowed certain transitions between states (see Figure 3-1 ).
Figure 3-1. Peripheral Transitions Between States
Figure 3-2 shows the flow needed to change the state of a given peripheral on the C6454 device.
Figure 3-2. Peripheral State Change Flow
A 32-bit key (value = 0x0F0A 0B00) must be written to the Peripheral Lock register (PERLOCK) in order to
allow access to the PERCFG0 register. Writes to the PERCFG1 register can be done directly without
going through the PERLOCK register.
NOTE
The instructions that write to the PERLOCK and PERCFG0 registers must be in the same
fetch packet if code is being executed from external memory. If the instructions are in
different fetch packets, fetching the second instruction from external memory may stall the
instruction long enough such that PERCFG0 register will be locked before the instruction
is executed.
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