Hi Wolfram,
On Tue, Mar 22, 2016 at 5:26 PM, Wolfram Sang <wsa@xxxxxxxxxxxxx> wrote:
>> However, the notes for Table 8.2a say there are _2_ possible values:
>>
>> "The initial value depend on MD14, MD13.
>> When MD14=L and MD13 = H, RCLK = 32.89 (kHz)
>> In the other setting, RCLK = 32.55 (kHz)
>
> Well, to be precise, it says the are two resulting frequencies, but for
> that, 4 values are needed as you found out.
>
>
>> While the register documentation says there are _4_ possible values, and it
>> doesn't document the relation behind these values and the "dividers":
>>
>> "MD14=0, MD13=0: 6’B00_1111
>> MD14=0, MD13=1: 6’B01_0010
>> MD14=1, MD13=0: 6’B01_0111
>> MD14=1, MD13=1: 6’B01_1111"
>>
>> I also cannot see how you get to the RCLK/OSCCLK values by using EXTAL
>> (33.33333 MHz on final boards) and the dividers above.
>
> See figure 8.1a. OSCCLK is EXTAL_divider / 8. Internal RCLK is
> EXTAL_divider / 8 / 4. So, now assume the lower 6 bits of the RCKCR
> register are a standard DIV6 divider where the divisor is the value of
> these bits + 1. So, with EXTAL = 33.333MHz and MD14=MD13=1, the register
> value becomes 0x1f and divisor = 32.
>
> So for internal RCLK: 33333333 / 32 (fixed prescaler) / 32 (DIV6) = 32552.1
>
> According to the Salvator-X manual, section 2.1.1.9:
>
> When EXTAL = 20MHz, and MD14=0 and MD13=1, then regval = 0x12, divisor = 19:
>
> So for internal RCLK: 20000000 / 32 (fixed prescaler) / 19 (DIV6) = 32894.7
>
> I tried all the combinations and they match the datasheet precisely.
Thanks for the explanation.
The numbers didn't match for me, as I had forgotten about the different
EXTAL value.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
