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Altera_Forum's avatar
Altera_Forum
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13 years ago

MAX II CPLD UFM speed

Oddly, a search for UFM on this forum did not return any hits. Sorry if this has already been discussed.

If I understand the documentation correctly I should be getting read times of about 65ns for speed grade 5 devices with 5MHz UFM clock per page 5-15 of MAXII device handbook:

tRA Maximum read access time 65 ns

I used megafunction wizard to add UFM in read only mode with parallel interface to my project. Per readings from my oscilloscope I'm getting data valid with about 6microsecond delay from initiating the read! Am I reading something wrong in the docs and this is to be expected or is something really wrong with my results?

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    From what I understand from figure 5-3, the address and data are clocked in/out serially. Could be wrong though. While I'd love to use the UFM, the additional 80LE overhead and the slow performance isn't worth it...

    Hope this helps...

    -Mux
  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    I think you're right. When I looked at block diagram of UFM it showed registers for both address and data. Since both serial and parallel access is available through megafunction I presumed that when in parallel access mode address and data is written/read as parallel to these registers. Now I think that megafunction converts it to serial data, clocks it into register serially and then uses it as parallel. Sounds like results that I'm getting are actually to be expected. That's not as exciting of a feature then as what I initially thought but still may be ok for some uses.

    Thanks for your response, Mux!
  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    Yup. Would be perfect for a boot-rom or microcode had it not been for the slow access time :-|

    -Mux
  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    In my view, UFM is perfect for storage of configuration and calibration parameters, that is read at configuration time and rewritten only occasionally rewritten, either by application code or external programmer. Speed is basically sufficient for this purpose.