Hi Marion,
Tony is correct about the trim value that needs to be programmed on each MCU. NXP stores an 8-bit trim value for the ICS at location 0xFFAF in flash on our production line. The fine trim bit (FTRIM) is stored in bit 0 of the 0xFFAE. These locations are erased during a production programming process, so the programming tool must know to read them before erasing, and then program them after the application code is programmed. The Cyclone Pro defaults to calculating the trim value and then programming it after the app is programmed. This can be seen in the Advanced Programming Options in one of the Cyclone Pro windows. You can uncheck the Calculate Trim box, and the Cyclone Pro will copy the value that NXP programmed to re-program that value after the flash is erased and programmed with the app code. However, it is always best to calculate the trim value in the application because this is more accurate (accounts for the system parasitics).
A generic programmer that does not check for the trim values will erase all flash and only program the app code. Our trim value will be lost. (0xFF, the value of an erased location, will cause the ICS to run slower if this is used as the trim value.) There are production programmers that can read the NXP factory trim values, but this is usually an option that the program house or test engineer needs to enable.
Please make sure that your code reads the 0xFFAF location and stores the data to the ICSTRM register, and then reads the 0xFFAE location and stores bit 0 to the ICSSC register. Otherwise, the internal oscillator will use a default trim value of 0x80 which may not give you the frequency you desired.
Regards,
John Suchyta
