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.