Re: about clock register setting

Pick up a C book, that is pretty basic. Dereference a pointer to an element
of structure and read the value, then do bitwise and with 0x1F, then compare
the result with 16.

--
Bruce Eitman (eMVP)
Senior Engineer
beitman AT applieddata DOT net

Applied Data Systems
www.applieddata.net
An ISO 9001:2000 Registered Company
Microsoft WEP Gold-level Member

"daniel" <daniel@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:0F83D30F-4274-45E7-9CA7-65EA85E394DF@xxxxxxxxxxxxxxxx
Thank you Bruce,

I feel I can understand the remaining code by referencing the cpu
data***
but the first if condition statement can't be understood.
if ((pCLKRegs->cccr & 0x1F) < 16)
What's the meaning of pCLKRegs->cccr & 0x1F ?



"Bruce Eitman [eMVP]" wrote:

Explaining line by line would take pages of information. Could you
narrow
it down by telling us what you don't understand?

I will give you a quick overview of what is going on.

1. You have a structure which maps to how the registers are layed out in
the hardware
2. You have a pointer to the structure
2. The pointer to the stucuture is mapped to the base address of some
part
of the hardware
3. By dereferencing the pointer to the strucutre, you are
reading/writitng
the register in hardware
4. The registers are defined in the PXA270 Developer's Manual where you
can
get all of the detail for the hardware.

--
Bruce Eitman (eMVP)
Senior Engineer
beitman AT applieddata DOT net

Applied Data Systems
www.applieddata.net
An ISO 9001:2000 Registered Company
Microsoft WEP Gold-level Member

"daniel" <daniel@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:4ADB7896-5EDB-4F8A-9B36-88359C02FB4E@xxxxxxxxxxxxxxxx
I'm not familiar with hardware register control.
During reading my pxa 27x BSP, I got reached a very hardware specific
code
about system clock manager setting like following.

// pCLKRegs is a Clock manager's address and cccr is Core Clock
Configuration register
if ((pCLKRegs->cccr & 0x1F) < 16)
{
// If do not change to 91Mhz, do not need to change mdrefr.
//pMEMC->mdrefr &= ~(0xFFF);
//pMEMC->mdrefr =
((0x1<<29)|(0x1<<20)|(0x1<<17)|(0x1<<16)|(0x1<<13)|0x31);
pMEMC->mdcnfg = 0xA000AC9;
pMEMC->mdrefr = 0x2013A031;
pMEMC->msc0 = 0x15D095D2;
}

Is there any kind teacher who will let me know the code line by line?
Or
introduce any material which I should first study.
Thank you in advance.





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