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UM10601
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© NXP B.V. 2012. All rights reserved.
Preliminary user manual
Rev. 1.0 — 7 November 2012
23 of 313
NXP Semiconductors
UM10601
Chapter 4: LPC800 System configuration (SYSCON)
4.6.7 System reset status register
The SYSRSTSTAT register shows the source of the latest reset event. The bits are
cleared by writing a one to any of the bits. The POR event clears all other bits in this
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.
4.6.8 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 12.
System reset status register (SYSRSTSTAT, address 0x4004 8030) bit description
Bit
Symbol
Value
Description
Reset
value
0
POR
POR reset status
0
0
No POR detected
1
POR detected. Writing a one clears this reset.
1
EXTRST
Status of the external RESET pin. External reset status.
0
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
-
Table 13.
System PLL clock source select register (SYSPLLCLKSEL, address 0x4004 8040)
bit description
Bit
Symbol
Value
Description
Reset
value
1:0
SEL
System PLL clock source
0
0x0
IRC
0x1
Crystal Oscillator (SYSOSC)
0x2
Reserved.
0x3
CLKIN. External clock input.
31:2
-
-
Reserved
-