2009-12-08 01:47:19     confusion about CLK of spi,uart,Fsclk

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2009-12-08 01:47:19     confusion about CLK of spi,uart,Fsclk

鹏 肖 (CHINA)

Message: 83185   

 

mike :

 

           after the uclinux  sets up, I get that the clk of the Uclinux  is 99.999Mhz.  But  when  I  am using the uart(serial )  to telnet the  uclinux,I  define the BAURD  115200.  So  the clk is 115200*8=921600

 

          99.999Mhz   are  divided  to  fit  the clk  921600.  but   they  are not  timed.

 

          however, the serial is working well.

 

Now, my question comes.  I  use the  BF561 spi  to send message  to another  prossor(MSP430).

 

  BF561       spi clk=Fsclk/(2*SPIbaud);

 

MSP430  clk =11.0592Mhz;      spi clk=11.0592M/a   (  frequency division  )

 

 

 

they are not timed .  Can the spi  work well?

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2009-12-08 02:21:17     Re: confusion about CLK of spi,uart,Fsclk

Sonic Zhang (CHINA)

Message: 83187   

 

SPI slave device is driven by the clock output from SPI master device. The SPI clock based on SCLK is not explicit equal to what you expect. But, SPI slave device can works well if the clock meets the spec.

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2009-12-08 05:02:09     Re: confusion about CLK of spi,uart,Fsclk

鹏 肖 (CHINA)

Message: 83237   

 

Sonic:

 

meets the spec??  what is the spec.

 

If  MSP430 is  working  under the slave mode,  do I need  to define  its clock?  Or I just  line  the 561's SCK   and the MSP430's clock    together?

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2009-12-08 05:36:11     Re: confusion about CLK of spi,uart,Fsclk

Michael Hennerich (GERMANY)

Message: 83238    >If MSP430 is working under the slave mode, do I need to define its

>clock?

 

No the clocks are only for Master Mode.

 

>Or I just line the561's SCKand the MSP430'sclock together?

 

Yes this is how SPI works. Synchronous Master -> Slave.

 

  docs.blackfin.uclinux.org/doku.php?id=spi

 

-Michael

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2009-12-08 20:41:49     Re: confusion about CLK of spi,uart,Fsclk

鹏 肖 (CHINA)

Message: 83260   

 

Michal:

 

Thanks. I  am trying again,

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2009-12-08 21:04:11     Re: confusion about CLK of spi,uart,Fsclk

鹏 肖 (CHINA)

Message: 83261   

 

Michal:

 

Because  I  think  there is only one slave device. So I did  not  select  the Slave Select Line.  Just use  three lines(SCK  MOSI  MISO).

 

 

 

Is  there  something wrong?

 

From   docs.blackfin.uclinux.org/doku.php?id=spi.     I  get  that: if  I  do not  use  the  mode0  and  mode2,  the slave select  line  is  not  needed  to  be  used?

 

My   conclusion  is  right  or  wrong?

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2009-12-08 21:09:10     Re: confusion about CLK of spi,uart,Fsclk

Mike Frysinger (UNITED STATES)

Message: 83262   

 

michael already told you -- master drives the clocks, slave watches the slave cs.  if the Blackfin is operating as the master, then you shouldnt have to screw with anything.  treat the MSP430 like any other slave device.

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