ARM Cortex R4F - Manual (Page 83)

Processor Initialization, Resets, and Clocking
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3.3.2 Processor reset
A processor or warm reset initializes the majority of the processor, excluding the
EmbeddedICE-RT logic. Processor reset is typically used for resetting a system that has been
operating for some time, for example, watchdog reset.
Because the nRESET signal is synchronized within the processor, you do not have to
synchronize this signal.
3.3.3 Normal operation
During normal operation, neither processor reset nor power-on reset is asserted. If the
Embedded ICE-RT is not used, the value of PRESETDBGn does not matter.
3.3.4 Halt operation
When nCPUHALT is asserted, and nSYSPORESET and nRESET deasserted, the processor
is out of reset, but the PFU is inhibited from fetching instructions. For example, you can use
nCPUHALT to enable DMA into the TCMs using the processor. You can then deassert
nCPUHALT and the PFU starts fetching instructions from TCMs. When the processor has
started fetching, nCPUHALT must not be asserted again except when the processor is reset.