SWT in MPC5674F

[rajiilangovan]

hi friend,

          What is meant by Hard lock and Soft lock in Software Watchdog Timer. Kindly tell Where i have use it both the locks?

[petervlna · Accepted solution]

Hi,

If either the HLK or SLK bits in the SWT_MCR are set then the SWT_MCR, SWT_TO, SWT_WN, SWT_SK registers are read only.

Hard Lock :

Can be only cleared by reset.

It is widely used when you configure peripheral and you want to be sure that no changes are accidentally made during SW run-time.

Soft Lock :

Can be cleared by SW. Soft lock is cleared by writing the unlock sequence to the service register.

Can be used whenever you need to change value in secured registers during run-time.

Use of this feature is strongly application specific.

Peter

[rajiilangovan]

hi,

       Thanks for your reply.i have one doubt. What is meant by unlock sequence? How can i write it? Is there any procedures to follow that unlock sequence?

[petervlna]

Hi Raji,

Try sometimes read the reference manual as the information you are asking are there.

Reference manual chapter 17.4 Functional Description:

The unlock sequence is a write of 0xC520 followed by a write of 0xD928 to the SWT_SR[WSC] field. There is no timing requirement between the two writes.

Peter

[rajiilangovan]

Thank you for your reply.i have another doubt.what is the difference  between software watchdog timer and MCU core watchdog timer?