MCBSTR9: RUNNING AT 96MHZ

Information in this article applies to:

• MCBSTR9 Evaluation Boards

QUESTION

Using the Keil BLINKY example for the MCBSTR9 board, everything runs OK at 24MHz, but when I change the PLL post-divider value (PLL_PDIV) from 3 to 2 in the STARTUP.S file to run at 96MHz, then download and run, the program does not run (no LEDs blink). What's wrong?

ANSWER

When you set the PLL post-divider value (PLL_PDIV) to 2, you must change the Clock Control Register (SCU_CLKCNTR) to the following:

• EMIRATIO: External Memory Interface Ratio fBCLK=HCLK/2
• FMISEL: Flash Memory Interface Clock Divider FMICLK=RCLK/2

Note:

This applies to earlier silicon revisions of STR91x which had a problem with System reset at 96MHz and it was not possible to use a 96MHz clock for FMI (see http://www.st.com/stonline/products/literature/es/12280.pdf page 12). This was fixed in STR91x Rev D with date code 618 and later and in STR91xFA.

SEE ALSO

• MCBSTR9: PFQBC (PREFETCH QUEUE) ENABLE IN STR91X.S

FORUM THREADS

The following Discussion Forum threads may provide information related to this topic.

• A contraction between Keil and ST documentation
• ARM: STR912 EV board

Last Reviewed: Wednesday, April 16, 2008