UM10462
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© NXP B.V. 2016. All rights reserved.
User manual
Rev. 5.5 — 21 December 2016
27 of 523
NXP Semiconductors
UM10462
Chapter 3: LPC11U3x/2x/1x System control block
3.5.9 Internal resonant crystal control register
This register is used to trim the on-chip 12 MHz oscillator. The trim value is factory-preset
and written by the boot code on start-up.
3.5.10 System reset status register
If another reset signal - for example the external RESET pin - remains asserted after the
POR signal is negated, then its bit is set to detected. Write a one to clear the reset.
applies to the POR reset.
3.5.11 System PLL clock source select register
This register selects the clock source for the system PLL. The SYSPLLCLKUEN register
(see
) must be toggled from LOW to HIGH for the update to take effect.
Table 15.
Internal resonant crystal control register (IRCCTRL, address 0x4004 8028) bit
description
Bit
Symbol
Description
Reset value
7:0
TRIM
Trim value
0x80 then flash will
reprogram
31:8
-
Reserved
0x00
Table 16.
System reset status register (SYSRSTSTAT, address 0x4004 8030) bit description
Bit
Symbol
Value
Description
Reset
value
0
POR
POR reset status
1
0
No POR detected
1
POR detected. Writing a one clears this reset.
1
EXTRST
External reset status
1
0
No reset event detected.
1
Reset detected. Writing a one clears this reset.
2
WDT
Status of the Watchdog reset
0
0
No WDT reset detected
1
WDT reset detected. Writing a one clears this reset.
3
BOD
Status of the Brown-out detect reset
0
0
No BOD reset detected
1
BOD reset detected. Writing a one clears this reset.
4
SYSRST
Status of the software system reset
0
0
No System reset detected
1
System reset detected. Writing a one clears this reset.
31:5
-
-
Reserved
-