PC87591L datasheet(169/437 Pages) NSC

Part #	PC87591L

Description	LPC Mobile Embedded Controllers

PDF	437 Pages

Scroll/Zoom	100%

Manufacturer	NSC [National Semiconductor (TI)]

Direct Link	http://www.national.com

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169 / 437 page

Embedded Controller Modules (Continued)

Revision 1.07

169

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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

WATCHDOG starts operating and must be touched periodically to prevent a WATCHDOG error signal.

4. Configure the WATCHDOG to use data match, and lock all the TWD configuration and setting registers by setting bits 0

through 4 and bit 6 of the TWCFG.

5. Touch the WATCHDOG by writing 5C16 to WDSDM at the appropriate rate (i.e., no more than once every WATCHDOG

clock cycle and no less than the period programed to WDCTL).

PC87591L Datasheet(PDF) 169 Page - National Semiconductor (TI)