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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
547 of 808
NXP Semiconductors
UM10360
Chapter 28: LPC17xx Watchdog Timer (WDT)
5.
Block diagram
The block diagram of the Watchdog is shown below in the
. The
synchronization logic (PCLK - WDCLK) is not shown in the block diagram.
Table 510: Watchdog Timer Clock Source Selection register (WDCLKSEL - address
0x4000 0010) bit description
Bit
Symbol
Value Description
Reset
Value
1:0
WDSEL
These bits select the clock source for the Watchdog timer as
described below.
Warning:
Improper setting of this value may result in incorrect
operation of the Watchdog timer, which could adversely affect
system operation. If the WDLOCK bit in this register is set, the
WDSEL bit cannot be modified.
0
00
Selects the Internal RC oscillator (irc_clk) as the Watchdog clock
source (default).
01
Selects the APB peripheral clock (watchdog pclk) as the
Watchdog clock source.
10
Selects the RTC oscillator (rtc_clk) as the Watchdog clock
source.
11
Reserved, this setting should not be used.
30:2 -
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
NA
31
WDLOCK 0
This bit is set to 0 on any reset. It cannot be cleared by software. 0
1
Software can set this bit to 1 at any time. Once WDLOCK is set,
the bits of this register cannot be modified.