What is 52233DEMO clock freq for 25MHz external crystal osc

[TVNAIDU]

I have 52233DEMO board, I can see 25MHz crystal on DEMO board, but DEMO user fuide says, it can run at 60MHz, with 25MHz crystal, is clock running at 60MHz?.

thanks,

Message Edited by TVNAIDU on 2009-11-11 04:25 AM

[mjbcswitzerland]

Hi

In the clock module the following are set:

- CCHR = 4 (divides the input frequency from 25MHz to 5MHz)

- SYNCR = 0x4007 (sets the PLL up to generate 60MHz internal clock)

Regards

Mark

[TVNAIDU]

Thanks.

PIT document referring Internel Bus clock below, Is Internal Bus clock is 60MHz (PLL Freq)?.  I have 52233DEMO, on that board, there is one 25MHz crystal, to calculate modulus value, if I set PRE to 8 (1000), then what clock speed I have to assume?.

The PIT’s timeout value is given here:

1/(Internal Bus clock) * 2(Prescaler Value+1) * Module Value = Time (seg).

[mjbcswitzerland · Accepted solution]

Hi

The "bus clock" is in fact half the PLL clock.

The following is a define to calculate the PIT using a 1k prescaler (where REQUIRED_MS is the value in ms):

#define TICK_DIVIDE (((PLL_CLOCK/2/1048) + REQUIRED_MS/2)/REQUIRED_MS)

See also http://forums.freescale.com/freescale/board/message?board.id=CFCOMM&message.id=726&query.id=57187#M7...

Regards

Mark