pc87591l National Semiconductor Corporation, pc87591l Datasheet - Page 164

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

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Embedded Controller Modules
4.10 TIMER AND WATCHDOG (TWD)
The Timer and WATCHDOG module (TWD) generates the clocks and interrupts used for timing periodic functions in the
system. It also provides WATCHDOG protection over software execution.
The TWD provides flexibility in system configuration by enabling the configuration of various clock ratios. After setting the
TWD configuration, the software can lock it to give a higher level of protection against erroneous software action. Once a
section of the TWD is locked, only reset releases it. See Figure 59 for the TWD block diagram.
4.10.1 Features
4.10.2 Functional Description
Input Clock
The TWD bases all its counting activities on a 32.768 KHz clock. The WATCHDOG can count using a division of the 32 KHz
clock (either T0OUT or T0IN).
32.768 KHz input clock
Programmable pre-scale counter
16-bit programmable periodic interrupt timer
8-bit WATCHDOG counter
WATCHDOG signal generation in response to failure detection, such as:
— WATCHDOG service performed too early
— WATCHDOG service performed too late
— Wrong DATA used in a service by data match
(DEV Env. only)
32.768 KHz
from RTC
FREEZE
Figure 59. Timer and WATCHDOG Block Diagram
WDCT0I bit (TWCFG Register)
(Continued)
5-Bit Pre-Scale
Counter
(TWCP)
TWDT0 Register
16-Bit Timer
164
WDSDM
WDCNT
WATCHDOG
T0IN
Peripheral Bus
WATCHDOG
Service
Logic
T0OUT
WATCHDOG
Signal
to Reset Circuit
to ICU
T0IN
to ACM
Revision 1.07