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gahelton1
gahelton1
Associate III
February 14, 2010
Question

Trace debugging and FSMC address lines

  • February 14, 2010
  • 2 replies
  • 729 views
Posted on February 14, 2010 at 17:55

Trace debugging and FSMC address lines

    This topic has been closed for replies.

    2 replies

    gahelton1
    gahelton1Author
    Associate III
    May 17, 2011
    Posted on May 17, 2011 at 13:40

    Well, I found my answer - In the datasheet of course.

    Here are the mappings.

    FSMC_A19        TRACED0

    FSMC_A20        TRACED1

    FSMC_A21        TRACED2

    FSMC_A22        TRACED3

    FSMC_A23        TRACECLK

    This was an unfortunate choice for pin mapping on ST's part. If order of trace pin mappings had been reversed, then additional address lines could have been used while preserving some level of synchronous trace debugging. Here is an example:

    FSMC_19        TRACED3

    FSMC_20        TRACED2

    FSMC_21        TRACED1

    FSMC_22        TRACED0

    FSMC_23        TRACECLK

    In this example, if single data line trace debugging was desired, then FSMC_A23 and FSMC_A22 would be taken for trace lines, but FSMC_A0-A21 would be free for external memory. Likewise if two data line trace debugging was desired, the FSMC_A23,A22,A21 would be used for trace lines, but FSMC_A0-A20 would be free for external memory.

    Alas, this is not the case. As soon as synchronous trace debugging is selected, FSMC_A19-A23 are now unusable as address lines (for any trace debugging width).

    From: helton.gregory

    Posted: Tuesday, February 16, 2010 6:05 PM

    Subject: Trace debugging and FSMC address lines

    The answer from ST is ''No''. Trace lines cannot be shared with FSMC lines.

    However, a new question comes to mind. There are reduced synchronous trace data width modes (1,2,4 bits). If only two trace bits are used, can the other FSMC line be used for external memory ?  Do the trace pins map in such a manner to make this possible ?

    A new request has been sent to ST for the answers. Answer will be posted here.

    gahelton1
    gahelton1Author
    Associate III
    May 17, 2011
    Posted on May 17, 2011 at 13:40

    The answer from ST is ''No''. Trace lines cannot be shared with FSMC lines.

    However, a new question comes to mind. There are reduced synchronous trace data width modes (1,2,4 bits). If only two trace bits are used, can the other FSMC line be used for external memory ?  Do the trace pins map in such a manner to make this possible ?

    A new request has been sent to ST for the answers. Answer will be posted here.

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