pc87591l National Semiconductor Corporation, pc87591l Datasheet - Page 166

• Manufacturer Part Number: pc87591l
• Description: Lpc Mobile Embedded Controllers
• Manufacturer: National Semiconductor Corporation

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Embedded Controller Modules
4.10.3 TWD Registers
For a summary of the abbreviations used for Register Type, see “Register Abbreviations and Access” on page 34.
TWD Register Map
Timer and WATCHDOG Configuration Register (TWCFG)
The TWCFG register is a byte-wide, read/write register. It defines the WATCHDOG clock input and service method and en-
ables TWD control register locking. Setting the required configuration and locking the TWCFG stops the software from in-
terfering with the WATCHDOG operation. On reset, non-reserved bits of TWCFG are initialized to 0.
Location: 00 FEE0
Type: R/W
Bit
Name
Reset
Bit
0
1
2
3
4
LTWCFG.
0: Enables read/write from/to TWCFG register
1: Any data written to it is ignored and reading from it returns unpredictable values
Once LTWCFG is set, it can only be cleared by reset.
LTWCP.
0: Enables read/write from/to TWCP register
1: Any data written to it is ignored and reading from it returns unpredictable values
Once LTWCP is set, it can only be cleared by reset.
LTWDT0.
0: Enables read/write from/to TWDT0 and T0CSR registers
1: Registers cannot be written to and TWDT0 cannot be read. Any data written to TWDT0 or T0CSR is ignored.
Once LTWDT0 is set, it can only be cleared by reset.
LWDCNT.
0: Enables write to WDCNT register
1: Any data written to it is ignored and reading from it returns unpredictable values
Once LWDCNT is set, it can only be cleared by reset. When WDSDME bit is cleared, touch operations (i.e.,
writing to WDCNT register) may be performed when LWDCNT bit is either 0 or 1.
WDCT0I.
0: Selects T0OUT clock as the WATCHDOG clock
1: Selects T0IN as the input clock
The hardware clock source selection overrides this clock selection.
Reading from TWDT0 returns unpredictable values.
TWCFG
TWCP
TWDT0
T0CSR
WDCNT
WDSDM
Mnemonic
16
7
0
Reserved
Timer and WATCHDOG Configuration Register
Timer and WATCHDOG Clock Pre-Scaler Register
TWD Timer 0 Register
TWDT0 Control and Status Register
WATCHDOG Count Register
WATCHDOG Service Data Match Register
6
0
WDSDME
(Continued)
5
0
Register Name
WDCT0I
Description
166
4
0
LWDCNT
3
0
LTWDT0
0
2
Type
R/W
R/W
R/W
R/W
WO
WO
LTWCP
1
0
LTWCFG
Revision 1.07
0
0