Classic/Legacy CodeWarriorのトピックRe: 56F8367 CW8.0 Problems with the SPI at 30 MHz

56F8367 CW8.0 Problems with the SPI at 30 MHz

rceit — Mon, 08 Oct 2007 15:23:35 GMT

Hi all,

I am trying to communicate two ADC’s from Analog Devices (one AD7676 and one AD7663) with a CPU 56F8367 by the SPI port. In fact, now I am using the MC56F8367EVME with the CodeWarrior 5.6.1.1658 and obviously programming with the Processor Expert beans. The ADC’s are connected in a daisy channel configuration in order to use only one SPI port in the DSP. In this configuration, the behaviour of both ADC is the same as only one. In fact, the clock of the DSP (obviously the master in my system is the DSP) drives both ADCs. The rise edge of the clock updates the output of the ADC (MOSI pin) and with the fall edge of the clock this updated data is being read.

When I adjust the speed of the SPI peripheral up to 15 MHz the system works properly. The problem appears when the clock is adjusted at 30 MHz. I have saw with the oscilloscope that the MOSI pin is correctly updated with the clock, but the SPI always have problems with the first bit. In fact at this speed, this first read bit always has the logical value of the MOSI before the actualization. Due to this bad behaviour always the correct string is shifted one bit to the right.

I have tested the configuration of the SPI (seeing the register values) and it seems that the processor expert is working properly.

This is my configuration

The chip select is always low

I start the process writing a word in the SPDTR register of the SPI. The idea is to activate the clock.

The transmission ends when the SPDRR is full (and obviously there is a flag that indicates this event)

CPHA = 1

CPOL = 0

Thank you very much, I am desperate

Re: 56F8367 CW8.0 Problems with the SPI at 30 MHz

trytohelp — Tue, 09 Oct 2007 21:59:44 GMT

Hi,

This is not easy to determine the cause of the problem.
The better way will be to log it directly in the Technical support system.
Please use Freescale on line support web page.
- Go to following URL: http://www.freescale.com/TechSupport
- Click on Submit a Service Request. You will come to a login page.
- You can submit your request through the web from there.

This request is more depending of the hardware.

I will probably forward it to the MCU team.

Pascal

Re: 56F8367 CW8.0 Problems with the SPI at 30 MHz

rceit — Tue, 16 Oct 2007 18:57:09 GMT

thanks Pascal, i will try your suggestion .Bye.

Re: 56F8367 CW8.0 Problems with the SPI at 30 MHz

dynapb — Wed, 14 Nov 2007 05:57:37 GMT

Hi,

Just a note for this. I was just reading the peripheral manual (rev 6), page 14-20, and it says that the SPI has a 20MHz limit.

Pete