PIC18F97J60 max external bus speed


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  1. #1
    Join Date
    May 2008
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    Unhappy PIC18F97J60 max external bus speed

    I've just managed to get this device working with external flash memory. I don't have timing diagrams of the external read and write cycles for the PIC, so tough to say what max bus speed I can operate at. I did see a comment in AN869 that the ext. bus speed is limited to 25MHz.

    Can anyone shed some light on this please?

    Mariusv

  2. #2
    skimask's Avatar
    skimask Guest

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    Quote Originally Posted by mariusv View Post
    I don't have timing diagrams of the external read and write cycles for the PIC, so tough to say what max bus speed I can operate at. I did see a comment in AN869 that the ext. bus speed is limited to 25MHz.
    Internet connection works...otherwise you wouldn't have been able to post a question.

    Is Microchip's website down?...otherwise you'd most likely be able to find the PIC18F97J60 datasheet possibly by searching for PIC18F97J60, or you might even click on this link:
    http://www.microchip.com/stellent/id...cName=en026439
    But since you've come this far and as you say, you have an example working with external flash memory, I think I can safely assume you know this already. I got the answer in less than a minute (excluding the download of the entire datasheet).

  3. #3
    Join Date
    May 2008
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    Thanks for your wonderful help, Skimask.

    I did find the datasheets, and it seems that the address valid to valid data time constraint was the most severe requirement. Using 70ns flash devices, I calculated that I could use a bus speed of 31.5MHz. However, the datasheet states that a bus speed of 25MHz should be used with external program memory.

    Has anyone done similar calcs?

    Thanks in advance
    Mariusv

  4. #4
    skimask's Avatar
    skimask Guest

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    Quote Originally Posted by mariusv View Post
    However, the datasheet states that a bus speed of 25MHz should be used with external program memory.
    I can't find that 'requirement' in the datasheets.
    Where are you seeing that?

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