EUSART vs. MSSP


Closed Thread
Results 1 to 10 of 10

Thread: EUSART vs. MSSP

  1. #1

    Default EUSART vs. MSSP

    I'm beginning a project and I can foresee it's going to need more I/Os than will be available on any one PIC. I've never used EUSART or MSSP before. I was wondering what the primary difference is between the two and why you would want to use one over the other. Pros and cons of the two? What are some examples of their best suited practical applications. I'm only at the brainstorming stage of this project, but I was thinking the secondary PIC(s) would only need to access the EEPROM of the primary PIC, so would MSSP probably be the best solution for that?

  2. #2
    Join Date
    Mar 2003
    Location
    Commerce Michigan USA
    Posts
    1,166


    Did you find this post helpful? Yes | No

    Default Re: EUSART vs. MSSP

    The Best and most concise explanation is in the particular data sheet for the processor you are planning on using. Visit MICROCHIP.com
    Dave Purola,
    N8NTA
    EN82fn

  3. #3
    Join Date
    Aug 2011
    Posts
    408


    Did you find this post helpful? Yes | No

    Default Re: EUSART vs. MSSP

    How many more IO's?

    If a larger pic doesn't fit the bill there are SPI/I2C 16-bit IO expanders like the MCP23017 that are infinitely easier to use than having to deal with the hassles of multiple pics and the interface between them. Plus they're cheap as dirt.

    Up to 8 expanders can be connected onto a single bus, so that's 8x 16 = 128 addt'l IO pins.

    Larger ones are available, but not from microchip.

  4. #4


    Did you find this post helpful? Yes | No

    Default Re: EUSART vs. MSSP

    Quote Originally Posted by tumbleweed View Post
    How many more IO's?

    If a larger pic doesn't fit the bill there are SPI/I2C 16-bit IO expanders like the MCP23017 that are infinitely easier to use than having to deal with the hassles of multiple pics and the interface between them. Plus they're cheap as dirt.

    Up to 8 expanders can be connected onto a single bus, so that's 8x 16 = 128 addt'l IO pins.

    Larger ones are available, but not from microchip.
    That's awesome! I didn't know such a thing existed. That will most likely be the best solution. Thanks. I'd still like to know more about the differences between MSSP and EUSART though. I'm just a noob teaching myself this stuff. I've read the datasheet, but they both kinda sound like they do roughly the same thing.

  5. #5
    Join Date
    Oct 2005
    Location
    Sweden
    Posts
    3,516


    Did you find this post helpful? Yes | No

    Default Re: EUSART vs. MSSP

    I'd still like to know more about the differences between MSSP and EUSART though
    EUSART = Enhanced Universal Asynchronous Receiver Transceiver
    MSSP = Master Synchronous Serial Port

    Asynchronous means there is no dedicated clock line/signal, while synchronous means there IS a clock line/signal. RS232 is an asynchronous communication standard while for example SPI and I2C are synchronous.

    /Henrik.

  6. #6


    Did you find this post helpful? Yes | No

    Default Re: EUSART vs. MSSP

    Quote Originally Posted by HenrikOlsson View Post
    EUSART = Enhanced Universal Asynchronous Receiver Transceiver
    MSSP = Master Synchronous Serial Port

    Asynchronous means there is no dedicated clock line/signal, while synchronous means there IS a clock line/signal. RS232 is an asynchronous communication standard while for example SPI and I2C are synchronous.

    /Henrik.
    Can you give me a practical example of where it would be beneficial to have a dedicated clock line and also to not have a dedicated clock line?

  7. #7
    Join Date
    Apr 2014
    Location
    OK
    Posts
    557


    Did you find this post helpful? Yes | No

    Default Re: EUSART vs. MSSP

    If you have 2 PIC processors clocked at the same Fosc talking to each other, Asynchronous saves the clock pin. However, if you are talking to a peripheral with no oscillator (internal or external), it needs a way to know when to look at the data pin (or port) to take a picture & extract the data. Here the clock pin is necessary. The clock pin also keeps timing issues clean when communicating between 2 devices that don't share the same Fosc. The faster the communication, the more critical timing becomes.

  8. #8
    Join Date
    Aug 2011
    Posts
    408


    Did you find this post helpful? Yes | No

    Default Re: EUSART vs. MSSP

    Synchronous devices typically latch the data on the clock edges, while async devices usually sense a change in the data,
    wait a bit, and then begin sampling the signal one or more times to determine the logic state.

    If you have long lines with mismatched impedance where the signals ring a lot, or a lot of delay/skew between the signals
    then you can get false or mis-timed clocks and the data is corrupted. Since sync depends on a clock edge it also tends to be more susceptible to noise.

    The delay in an async scheme allows time for the signal to settle giving you a better chance of reading the data correctly.

  9. #9
    Join Date
    Dec 2010
    Posts
    409


    Did you find this post helpful? Yes | No

    Default Re: EUSART vs. MSSP

    In practical terms, the device you want to talk to usually determines. If you are talking to a computer it will likely be RS-232 serial port you need the EUSART. If you are designing both ends, use whatever you like.

  10. #10


    Did you find this post helpful? Yes | No

    Default Re: EUSART vs. MSSP

    That helps a lot. Thanks guys!

Similar Threads

  1. EUSART's - Which timers do they use?
    By Christopher4187 in forum mel PIC BASIC Pro
    Replies: 1
    Last Post: - 2nd June 2015, 00:06
  2. Any different between USART and EUSART?
    By Demon in forum Off Topic
    Replies: 1
    Last Post: - 2nd February 2014, 10:04
  3. Replies: 18
    Last Post: - 30th July 2012, 11:00
  4. Eusart?
    By rastan in forum mel PIC BASIC Pro
    Replies: 2
    Last Post: - 27th January 2005, 23:50
  5. Mssp
    By capitano in forum Code Examples
    Replies: 2
    Last Post: - 15th December 2004, 20:33

Members who have read this thread : 2

You do not have permission to view the list of names.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts