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Last Post 24 Jan 2006 11:23 AM by  Krispin Leydon
Wait states in LogicLoader
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aaronjstewart@gmail.com



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07 Dec 2005 04:51 PM
    I'm interested in the prospect of adding read cycle "wait states" to simulate the effects of having slower memory than is currently on the development board, but I encounter something odd when I try to change the number of wait states.

    At the LoLo command prompt, if I type the line:

    "x 0xFFFF1008"

    to examine the contents of the Bank 2 Control Register, I discover that it contains the value 0x10000c21 - not the default value in Sharp's manual for the chip.

    If I then enter the command:

    w 0xFFFF1008 0x10000FE1

    to *increase* the number of wait states (but otherwise leave the register's bits intact), I find that I can't subsequently load code into SRAM.

    What is going on?

    Is it naive to think that one can slow the system down by adding read cycle wait states?

    Does LoLo have particular requirements regarding the number of wait states?

    Anonymous





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    07 Dec 2005 04:57 PM
    Hello,

    At the speed that you're describing ' load elf ' can not keep up with the byte stream being sent. The solution is tp slow down the wait states after the load.

    Your procedure should be as follows:

    1) Load program using load command.

    2) use w command to set desired wait states

    3) use jump or exec command to start the code

    It is expected that we won't be able to keep up with the file when you slow down the processing to this degree. It's also good to remember that LogicLoader still has to service the tick interrupt every ms.

    It can't be expected that software will be independent of the speed of memory, because of this there is no reason to increase the wait states prior to jumping to his application.

    You may have to increase the wait states on turnaround time in order to better represent the performance degradation you can expect with slower SRAM. I would recommend consulting the SRAM data sheet for what that increase needs to be. We don't use burst mode, so the wst2 setting probably has no effect. It would be a good idea to consult all of the Sharp errata to make sure.

    Thanks,

    Krispin Leydon



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    09 Dec 2005 05:54 PM
    Hi,

    Posted By aaronlpd on 18 Nov 2004 7:57 AM


    It''s also good to remember that LogicLoader still has to service the tick interrupt every ms.





    Is this true if you are executing code with "exec" -- or only if you are using "jump"?

    If this is true: where can I learn more about what LoLo is doing while my code is executing? (I've read the Logic Loader user manual; I just want to make sure I'm not missing any resources...)

    Thanks!

    -Krispin

    Anonymous





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    24 Jan 2006 11:16 AM
    Krispin,

    You can also check out the LogicLoader User's Manual Addendums.

    Thanks,

    Krispin Leydon



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    24 Jan 2006 11:23 AM
    Thanks! I'll have a look.

    -Krispin
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