pc87591l National Semiconductor Corporation, pc87591l Datasheet - Page 169

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

Revision 1.07
Embedded Controller Modules
4.10.4 Usage Hints
The TWD protects WATCHDOG operation from software tampering. To achieve the highest level of protection, proceed as
follows:
1. Program the TWDT0 pre-scale and TMWT0 timers to the desired values.
2. Configure the WATCHDOG clock to use T0IN or T0OUT using WDCT0I bit in TWCFG register.
3. Program the WDCTL to the maximum period between WATCHDOG touch operations. Note that from this point, the
4. Configure the WATCHDOG to use data match, and lock all the TWD configuration and setting registers by setting bits 0
5. Touch the WATCHDOG by writing 5C
WATCHDOG starts operating and must be touched periodically to prevent a WATCHDOG error signal.
through 4 and bit 6 of the TWCFG.
clock cycle and no less than the period programed to WDCTL).
16
to WDSDM at the appropriate rate (i.e., no more than once every WATCHDOG
(Continued)
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