QEIWRM Chapter 5.6 says - " The BRG clock frequency is half the QUICC Engine clock divided by this combined source-clock factor.", so what is 'combined source-clock factor', how can I get the value of it?

Thanks

Jia

QEIWRM Chapter 5.6 says - " The BRG clock frequency is half the QUICC Engine clock divided by this combined source-clock factor.", so what is 'combined source-clock factor', how can I get the value of it?

Thanks

Jia

Have a great day,The BRG provides a divide-by-16 option (BRGCn[DIV16]) and a 12-bit prescaler (BRGCn[CD]) to divide the source clock frequency. As combined source-clock factor they mean the BRG division factor (D) i.e. ratio of BRG input and output clock frequencies. Its value is given by expression

If BRGCx[DIV16]=1 then D = 16*(BRGCx[CD] + 1)

If BRGCx[DIV16]=0 then D = BRGCx[CD] + 1

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-------------------------------------------------------------------------------Hi Serguei,

Thanks for reply!

The device tree file in linux defined 'brg-frequency', 'bus-frequency', I believe 'bus-frequency' denotes qe clock frequency, and I just want to get the correct value of 'brg-frequency'. Is 'BRG clock frequency' mentioned above equal to baud rate, such as 115200 in case of ucc_uart? What is the 'source clock frequency'? Is it derived from qe clock?

An comment in linux kernel @ucc_uart.c also says:

"Older versions of U-Boot do not initialize the brg-frequency property, so in this case we assume the BRG frequency is half the QE bus frequency."

I'm still confused anyway:-(

Thanks

Jia

Have a great day,

The BRG provides a divide-by-16 option (BRGCn[DIV16]) and a 12-bit prescaler (BRGCn[CD]) to divide the source clock frequency. As combined source-clock factor they mean the BRG division factor (D) i.e. ratio of BRG input and output clock frequencies. Its value is given by expression

If BRGCx[DIV16]=1 then D = 16*(BRGCx[CD] + 1)

If BRGCx[DIV16]=0 then D = BRGCx[CD] + 1

-------------------------------------------------------------------------------

Note:

- If this post answers your question, please click the "Mark Correct" button. Thank you!

- We are following threads for 7 weeks after the last post, later replies are ignored

Please open a new thread and refer to the closed one, if you have a related question at a later point in time.

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