Hi Fonze Actually the SPI protocols are similar except that in true SPI the clocks halt when the /CS (Frame Synch) is inactive. If this is important, you can manualy manipulate the FS/CLK lines by directly writing to these pins as bit IO at a rate up to F/2 or 37Mb/s for the 75 MIP VC33-150 (the serial port still works even though the pins are configured for IO). Another option is to use the DMA to 'burp out' the FS/CLK pattern you want. Clock, frame and data polarity, edge selection, idle hi/lo etc... are then just configuration bits in the serial port. You may also find that if your SPI devices have /SS pins, they will go high-Z when not selected. This would then allow you to hang multiple devices on one serial port. Otherwise, you are right... there is only one serial port. One word of caution regarding programmable IO. Resist the temptation to directly tie the FSX/FSR CLKX/CLKR lines together. Being programmable, IO pins are easily misconfigured or power up in undesired modes. Taje notice of the fact that most programmable IO on devices like the VC33 do not come with hardwired and therefor purely combinatorial hi-z pins. The solution is simply to add a small series resistor. A side benefit is that the series resistor also helps to match up the pin driver Z-out to the transmission line so you end up with cleaner signals :-) Best regards, Keith Larson ----------------------------- Fonze wrote: Hi Keith, Thank you very much for your enthusiasm. I had a glance to your TMS320VC33. It could effectively be quite easier to develop my application in floating point, and the TMS320VC33 would be perfect for this. The problem is it has no peripherals as SPI ports, just one serial. Best regards S.Castoldi +------------------------------------------+ |Keith Larson | |Member Group Technical Staff | |Texas Instruments Incorporated | | | | 281-274-3288 | | k-larson2@ti.com | |------------------------------------------+ | TMS320C3x/C4x/VC33 Applications | | | | $150 TMS320VC33 DSK's ARE AVAILABLE NOW | | | | TMS320VC33 | | The lowest cost and lowest power | | floating point DSP on the planet! | | 500uw/Mflop | +------------------------------------------+
searching for a low power DSP, about 80 MIPS with flash and A/D's
Started by ●September 3, 2003
Reply by ●September 10, 20032003-09-10