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UM10375
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 3 — 14 June 2011
30 of 368
NXP Semiconductors
UM10375
Chapter 3: LPC13xx System configuration
3.5.27 WDT clock source select register
This register selects the clock source for the watchdog timer. The WDTCLKUEN register
(see
) must be toggled from LOW to HIGH for the update to take effect.
Remark:
When switching clock sources, both clocks must be running before the clock
source is updated. Once the WWDT (LPC1311/01 and LPC1313/01 only) is enabled, the
watchdog clock source cannot be changed. If the watchdog timer is running in Deep-sleep
mode, always select the watchdog oscillator as clock source (see
).
3.5.28 WDT clock source update enable register
This register updates the clock source of the watchdog timer with the new input clock after
the WDTCLKSEL register has been written to. In order for the update to take effect at the
input of the watchdog timer, first write a zero to the WDTCLKUEN register and then write
a one to WDTCLKUEN.
Remark:
When switching clock sources, both clocks must be running before the clock
source is updated.
3.5.29 WDT clock divider register
This register determines the divider values for the watchdog clock wdt_clk.
Table 34.
WDT clock source select register (WDTCLKSEL, address 0x4004 80D0) bit
description
Bit
Symbol
Value
Description
Reset
value
1:0
SEL
WDT clock source
0x00
0x0
IRC oscillator
0x1
Main clock
0x2
Watchdog oscillator
0x3
Reserved
31:2
-
-
Reserved
0x00
Table 35.
WDT clock source update enable register (WDTCLKUEN, address 0x4004 80D4)
bit description
Bit
Symbol
Value
Description
Reset value
0
ENA
Enable WDT clock source update
0x0
0
No change
1
Update clock source
31:1
-
-
Reserved
0x00
Table 36.
WDT clock divider register (WDTCLKDIV, address 0x4004 80D8) bit description
Bit
Symbol
Description
Reset value
7:0
DIV
WDT clock divider values.
0: Disable WDCLK.
1: Divide by 1.
to
255: Divide by 255.
0x00
31:8
-
Reserved
0x00