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USI Vs USCI

A46810
Intellectual 560 points

Other Parts Discussed in Thread: MSP430FG4618

Hi,

I will be using a a 12 bit ADC and need to send this data to another MCU using SPI. As far as I understand the USCI only supports 8or 7 bits data transmission would it be better to send the data in 2 cycles using USCI or send it in 16 bit mode using USI. Which one would be more fast and efficient ?

 

  • 0
    Guru 58965 points

    As far as I know, only some of the F2xx and G2xx1 chips have USI and they do not have 12-bit ADC. What chip are you using?

     

  • 0 in reply to old_cow_yellow
    Intellectual 560 points

    Well I have the MSP430FG4618/F2013 experimenter board for now My basic aim was to use ADS 1298 24 bit ADC send digital data via SPI to either of FG4618/F2013/F5525

    I am more keen on F5525 since it has an onboard USB connection to send final data to my PC  but apart from the F2013 none have the USI so they can only send 8 bit data at a time,

    What is your recommendation ? I want it to develop a real time system and time stamps are very important.

  • 0 in reply to A46810
    Guru 227245 points

    None of the SPi devices I've seen so far uses any SPI transfer with a different bit size than 8 bits (16/24/32). except for a discontinued HF tuner chip. And even this chip accepted a 24 bit transfer and just took the last 21 bits of the transfer when CS got high again.
    So the capability of the USI to transfer any number of bits is mostly useless. The 16 bit register size is nice - if you have word-sized transfers always. But most devices which take 16 bit values, require 8 bit transfers too.
    Together with the fact that most MSPs don'T have an USI but rather an USCI or USART chip (which supports only 8 bit transfers) I'd use the USI, if at all, only in compatible 8 bit mode and do no special handling of non 8-bit aligned data.

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