Thomas Gaffney

Assembly to machine code timing

Discussion created by Thomas Gaffney on Jul 13, 2007
Latest reply on Jul 19, 2007 by MIKE YETSKO
I have a question about how long an assembly operation actually takes to execute on the S12X core processor.  I am using an MC9S12XDP512 chip with a 20 MHz oscillator.
 
I have a process that is interfacing with an FPGA and speed is an issue.  I placed a testbench signal that raises a pin high before this process starts and is set low once the process is done.  When looking at this pin on the scope, the process took much longer than I expected.
 
After this, I placed this testbench around two assembly statments.  The testbench signal was on for approximately 1 microsecond which seems very high.
 
Anyways, I know that assembly to machine code is not a direct 1-to-1 translation but this timing seems more like a 1-to-10 relationship.  Is this correct or am I missing something.
 
Finally, the clock and all clock monitors in the CRG are good and reporting no errors with the clock (I thought this might be caused by entering the self clock mode but this is not the case).
 
Thanks,
 
Thomas

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