topic Re: Regarding PMF register write protection in S12 / MagniV Microcontrollers

Regarding PMF register write protection

pratibhasurabhi — Sat, 23 May 2020 06:58:12 GMT

Hi All,

I am referring the MC9S12ZVM-Family RM.

15.8.1.1 Register Write Protection, note mentions -

Make sure to set the write protection bit WP in PMFCFG0 after configuring
and prior to enabling PWM outputs and fault inputs.

Query is whether this write protect [WP] feature is used to avoid writing on those registers by user or to avoid spurious writes[ not from user code].

My understanding is that once these write protect registers are initialised in the Init sequence, they are not written over again.

Thank you in advance.

Re: Regarding PMF register write protection

lama — Mon, 25 May 2020 05:51:59 GMT

Hi,

the note is a friendly warning. If you have read the description of the WP bit then you have seen the last and by my opinion critical sentence which says you that there is no place for mistake:

Write Protect— This bit enables write protection to be used for all write-protectable registers. While clear, WP
allows write-protected registers to be written. When set, WP prevents any further writes to write-protected
registers. Once set, WP can be cleared only by reset.

Best regards,

Ladislav