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SAMA5: Correct the PLL 48MHz divisor. It was off by a factor of two... no idea why

This commit is contained in:
Gregory Nutt 2013-08-14 19:38:48 -06:00
parent 0098c9ec5f
commit 371639637f
2 changed files with 7 additions and 5 deletions
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10
configs/sama5d3x-ek/include/board_384mhz.h
View File

@ -90,9 +90,9 @@
* NOTE: Bit PLLADIV2 must always be set to 1 when MDIV is set to 3.
*
* Prescaler input = 768MHz / 2 = 384MHz
* Prescaler output = 768MHz / 1 = 384MHz
* Prescaler output = 384MHz / 1 = 384MHz
* Processor Clock (PCK) = 384MHz
* Master clock (MCK) = 396MHz / 3 = 129MHz
* Master clock (MCK) = 396MHz / 3 = 128MHz
*/
#define BOARD_PMC_MCKR_CSS PMC_MCKR_CSS_PLLA
@ -126,11 +126,13 @@
* = 15
*
* The maximum value of USBDIV is 15 corresponding to a divisor of 16.
* REVISIT: USBDIV = 15 gives an exact clock of 48MHz.
* REVISIT: However, using the divisor of (15+1) yields a frame rate
* of 500 frames per second. A divisor of (7+1) gives the correct 1MS
* frame rate. I cannot explain the factor of 2 difference.
*/
#define BOARD_OHCI_INPUT PMC_USB_USBS_PLLA
#define BOARD_OHCI_DIVIDER (15)
#define BOARD_OHCI_DIVIDER (7)
/* Resulting frequencies */

2
configs/sama5d3x-ek/include/board_396mhz.h
View File

@ -89,7 +89,7 @@
* NOTE: Bit PLLADIV2 must always be set to 1 when MDIV is set to 3.
*
* Prescaler input = 792MHz / 2 = 396MHz
* Prescaler output = 792MHz / 1 = 396MHz
* Prescaler output = 396MHz / 1 = 396MHz
* Processor Clock (PCK) = 396MHz
* Master clock (MCK) = 396MHz / 3 = 132MHz
*/