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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
48 of 571
NXP Semiconductors
UM10316
Chapter 4: LPC29xx Reset Generation Unit (RGU)
Generation of reset outputs is controlled using registers RESET_CTRL0 and
RESET_CTRL1. Note that a POR reset can also be triggered by software.
The RGU monitors the reset cause for each reset output. The reset cause can be
retrieved with two levels of granularity.
The first level is monitored by the RESET_STATUS0 to 3 registers and indicates one of
the following reset causes (see
to
):
•
No reset has taken place
•
Watchdog reset
•
Reset generated by software via RGU register
•
Other cause
The second level of granularity is monitored by one individual register for each reset
output in which the detailed reset cause is indicated (see
).
Detailed reset causes depend on the reset hierarchy:
•
POR reset (does not have a reset source register as it can only be activated by POR)
•
RGU reset
•
Watchdog reset
•
PCR (Power control, Clock, and Reset Subsystem) reset
•
Cold reset
•
Warm reset
3.1 Reset hierarchy
The different types of system reset can be ordered according to their scope. The hierarchy
is as follows (see
):
1. POR reset: resets everything in the IC.
2. External reset: resets everything in the IC except the OSC 1M oscillator.
3. RGU reset: resets RGU and then has the same effect as Watchdog reset.
4. Watchdog-triggered reset: triggers PCR reset.
5. PCR reset: triggers cold reset and resets Watchdog and flash controller
general-purpose outputs.
6. Cold reset: triggers warm reset and resets external memory controller, flash controller,
SRAM controller, the SCU, and the CFID.
7. Warm reset: Resets non-memory peripherals (UART, ADC, I2C, timers, etc.). Does
not
reset memory controllers, SCU, CFID or Watchdog.
QEI_RST
WARM_RST
Quadrature encoder
DMA_RST
WARM_RST
GPDMA controller
USB_RST
WARM_RST
USB controller
VIC_RST
WARM_RST
Vectored Interrupt Controller (VIC)
AHB_RST
WARM_RST
CPU and AHB Bus infrastructure
Table 31.
Reset output configuration
…continued
Reset output
Reset source
Parts of the device reset when activated