12.4.20. Device Power Down and Reset Control Register

The PRCR is a read/write register that controls reset and power-down related functionality.

Figure 12.17 shows the bit arrangement of the PRCR.

Figure 12.17. PRCR format


Table 12.30 shows how the bit values correspond with the Device Power Down and Reset Control Register functions.

Table 12.30. PRCR bit functions

BitsFieldFunction

[31:3]

-Reserved. RAZ, SBZP.

[2]

Hold internal reset

Hold internal reset bit. This bit prevents the processor from running again before the debugger detects a power-down event and restores the state of the debug registers in the core power domain. This bit is also used to detect a reset (ARESETn) event. By examining PRSR[1], the debugger can determine whether a power-down or a reset event occurred. The effect of this bit is that if it is set to 1 and a processor reset occurs, ARESETn or nPORESET, then the processor behaves as if ARESETn is still asserted, until the debugger clears PRCR[2] to 0. This bit does not have any effect on initial system power up as PRESETn clears it to 0:

0 = does not hold internal reset on power up or reset, reset value

1 = holds the processor nondebug logic in reset on power up or reset until this bit is cleared to 0.

[1]

-Reserved. RAZ, SBZP.

[0]

No power down

No power down. When set to 1, the DBGNOPWRDWN output signal is HIGH. This output is connected to the system power controller and is interpreted as a request to operate in emulate mode. In this mode, the core and ETM are not actually powered down when requested by software or hardware handshakes. This mode is useful when debugging applications on top of working operating systems:

0 = DBGNOPWRDWN is LOW, reset value

1 = DBGNOPWRDWN is HIGH.


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