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You need to operate the McBSP in clock-stop (SPI) mode. Set it up as SPI slave device it will use external frame/clock/data inputs from your serial device. I remember seeing waveforms in the book showing how to set up the start bit timing relative to clock, etc. If you're not in clock-stop mode, the clock must be running continuously (or at least several cyles previous to the data receive) as you've discovered. In clock-stop mode the clock is only running during data transmission/reception. -George > From: Jagdish prasad <> > Subject: Observation > > Hi all, > I was working on serial interface(MCBSP) of DSP C5410. And was trying to > transmit/receive data from another device serial device. MCBSP serial port > assumes that clocks should always be present, not only when data is present. > We came to this conclusion by looking figures in the documents. Becausae it > is not mentioned any where in the document. We refered Enhance Peripherals > document (spru320.pdf). > My serial device which is communicating to DSP give the clock and data at > the same time. When the data is not present it stop the clock. I configured > DSP serial interface(MCBSP) to take clock&frame sync as input from external > source. > > Just after initializtion of receiver and transmitter of MCBSP, I gave data > as wel as clock . It looses first 2 bit, so second word's 2 bit msb becomes 2 > bit lsb of first word. same thing repeated afterwords. |
Re: Observation [McBSP]
Started by ●July 19, 2002
