Adam Jackson

FLL Oscillator Frequency Changes For No Reason? - mc9s08qe128

Discussion created by Adam Jackson on Jul 29, 2008
Latest reply on Aug 8, 2008 by Fabio Pereira


I am currently using a mc9s08qe128, I have it configured to use the FLL, the reference clock is set to the internal 32.768k.  DRS = 00, DMX32 = 1, I should have a DCO frequency of 19.92Mhz.  Every time I reset the board through P&E True-Time Sim, I get a differnt clock!

Frequency change to ~9491227hz.
Frequency change to ~9858172hz.
Frequency change to ~9832800hz.
Frequency change to ~9467767hz.

Why is this?  Is this just the inaccuracy of the interal reference?  My ICS setup rountine is:

            lda     #%00000111  ; FLL out sel'ed, 32.768k, int.ref. sel and EN'd,
            sta     ICSC1       ; Bus = div1, FEI Mode, Internal CLK
            lda     #%00001100
            sta     ICSC2
            lda     #%00110000  ; Low range, DMX32=1 => 19.92MHz Clock
            sta     ICSSC




Added p/n to subject.

Message Edited by ajacks504 on 2008-07-29 08:20 PM

Message Edited by NLFSJ on 2008-07-30 02:18 PM