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LPC1788 SSP maximum speed

ali micro

Hi
I have simple question about lpc1788:

*. what's the maximum bit rate of LPC1788 SSP?

maybe it's duplicated question but I need to be sure because I wanna buy and design new board and SSP bit rate is critical for me

more than 30Mbps is OK for me.

thanks in advance

Parents
  • 0 in reply to Alexan Eramian

    Hi
    in datasheet mentioned this number should be between 2-245 and even

    where is "8"?

    there is no any other fast serial protocol for lpc1788 about 30mbps or more?

    I should connect it to spartan3 FPGA and this speed is awful. I don't have enough GPIO in FPGA and MCU and I must to transfer data between those, about 4MBps.

    thanks a lot

Reply
  • 0 in reply to Alexan Eramian

    Hi
    in datasheet mentioned this number should be between 2-245 and even

    where is "8"?

    there is no any other fast serial protocol for lpc1788 about 30mbps or more?

    I should connect it to spartan3 FPGA and this speed is awful. I don't have enough GPIO in FPGA and MCU and I must to transfer data between those, about 4MBps.

    thanks a lot

Children
  • 0 in reply to ali micro

    You are absolutely right , the minimum divider of 8 is the case for the SPI peripheral and not the SSP.

    Note that a value of 255 is not possible because only even numbers should be used which means up to 254.

    Alex

  • 0 in reply to Alexan Eramian

    ;-(
    So...!!!
    which one is correct?
    minimum=8 or 2

    SPI or SSP can transmit up to what?

  • 0 in reply to ali micro

    SPI can transmit up to core_clock/8 and SSP core_clock/2.

    Alex

  • 0 in reply to Alexan Eramian

    you mean LPC1788 on SSP can transmit up to 60Mbps without any limitation.

    I knew I should observe a lot of things to make such a high speed connection about PCB design and etc but is it possible to gain more than 30mbps or IO pins can't toggle with such a speed (rising time and falling time or else doesn't limit these signals).

    would you please do me a favor: config SSP to maximum speed and with Oscilloscope check it whether the signals are correct or have Distortion.

    because I should select a powerful MCU with high speed SPI or SSP and if LPC1788 can satisfy me then I can buy it.

    I'll appreciate you.

    thanks

  • 0 in reply to ali micro

    Let me rephrase, according to the datasheet the max SSP clock is core_clock/2.

    Even if it is possible to get such a rate externally it would not leave much cpu time to do anything that send spi.

    Let me also add that in the following link it says
    ics.nxp.com/.../

    Q : What is the maximum SSP speed on the LPC17xx?
    A : The maximum SSP speed (in master mode) is pclk/2. The maximum clock (CCLK) of the LPC17xx can be set to 100MHz and, since the peripheral clock (PCLK) can be equal to CCLK, the maximum SSP rate (master mode) will be 50 Mbit/sec (100MHz/2). In Slave mode, the SSP clock rate provided by the master must not exceed 1/12 of the SSP peripheral clock (selected in peripheral clock selection register). The content of the SSPnCPSR register is not relevant. So, the maximum SSP speed (in slave mode) will be 8Mbit/sec.

    Alex

  • 0 in reply to Alexan Eramian

    thanks Alex , you are so fast to response
    that's so good information

    thanks thanks thanks