Flash clock generator divisor for 8 MHz ?

Raj P

Hi,

I am confused reading datasheet regarding divisor factor required for 8MHz in setting up flash generator on MSP430G2xx3 MCU.

For 8 MHz if I divide 32 , I get ~250 KHz while if I divide by 16 I get 500 KHz , but according to data sheet it recommends 257-476 KHz frequency. I am fixed with what value I should use ?

Does FN5 means divide by 64?

Can anyone please help me in formula which provides required flash generator divisor factor for 8 MHz

Thanks

over 12 years ago

0 old_cow_yellow over 12 years ago

Guru 58965 points

If the clock you selected is 8MHz, you need to divide it by an integer between 17 and 31. That means you need to set FN between 16 and 30.

FN is a 6-bit binary number. FN5 is BIT5 and equals 32. By itself without any of the other 4 bits, this means divide by 33 (too big for your use). I think:

FN4+FN2+FN1+FN0 (binary 010111, decimal 23) is suitable for you and will divide 8MHz by 24.

0 zrno soli over 12 years ago

Guru 34773 points

Raj P said:

For 8 MHz if I divide 32 , I get ~250 KHz while if I divide by 16 I get 500 KHz , but according to data sheet it recommends 257-476 KHz frequency. I am fixed with what value I should use ?

http://forum.43oh.com/topic/2972-sbw-msp430f550x-based-programmer/page-3#entry40359

; Setup flash clock 8 MHz / 17 = 470588 Hz
mov.w #(FWKEY + FSSEL1 + 16), &FCTL2 ;mov.w #(0A540h + 16), &FCTL2

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Flash clock generator divisor for 8 MHz ?