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soc: stm32f4xx: Document the flash latency values

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Document the flash latency values by copying the relevant tables
from the reference manuals for each MCU.

Change-Id: Ieb2824ffd7634d917399e3e62146d9243b527f44
Signed-off-by: Christer Weinigel <christer@weinigel.se>
This commit is contained in:
Christer Weinigel 2017-01-29 10:33:15 +01:00 • committed by Kumar Gala
commit 89c23e1c72
1 changed files with 49 additions and 1 deletions
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50
arch/arm/soc/st_stm32/stm32f4/flash_registers.h
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@ -51,7 +51,55 @@ struct stm32f4x_flash {
/**
* @brief setup embedded flash controller
*
* Configure flash access time latency depending on SYSCLK.
* Configure flash access time latency (wait states) depending on
* SYSCLK. This code assumes that we're using a supply voltage of
* 2.7V or higher, for lower voltages this code must be changed.
*
* The following tables show the required latency value required for a
* certain CPU frequency (HCLK) and supply voltage. See the section
* "Relation between CPU clock frequency and Flash memory read time"
* in the reference manual for more information.
*
* Note that the highest frequency might be limited for other reaasons
* than wait states, for example the STM32F405xx is limited to 168MHz
* even with 5 wait states and the highest supply voltage.
*
* STM32F401xx:
*
* LATENCY | 2.7V - 3.6V | 2.4V - 2.7V | 2.1V - 2.4V | 1.8V - 2.1V
* ------- | ----------- | ----------- | ----------- | -----------
* 0 | 30 MHz | 24 MHz | 18 MHz | 16 MHz
* 1 | 60 MHz | 48 MHz | 36 MHz | 32 MHz
* 2 | 84 MHz | 72 MHz | 54 MHz | 48 MHz
* 3 | | 84 MHz | 72 MHz | 64 MHz
* 4 | | | 84 MHz | 80 MHz
* 5 | | | | 84 MHz
*
* STM32F405xx/407xx/415xx/417xx/42xxx/43xxx:
*
* LATENCY | 2.7V - 3.6V | 2.4V - 2.7V | 2.1V - 2.4V | 1.8V - 2.1V
* ------- | ----------- | ----------- | ----------- | -----------
* 0 | 30 MHz | 24 MHz | 22 MHz | 20 MHz
* 1 | 60 MHz | 48 MHz | 44 MHz | 40 MHz
* 2 | 90 MHz | 72 MHz | 66 MHz | 60 MHz
* 3 | 120 MHz | 96 MHz | 88 MHz | 80 MHz
* 4 | 150 MHz | 120 MHz | 110 MHz | 100 MHz
* 5 | 180 MHz | 144 MHz | 132 MHz | 120 MHz
* 6 | | 168 MHz | 154 MHz | 140 MHz
* 7 | | 180 MHz | 176 MHz | 160 MHz
* 8 | | | 180 MHz | 168 MHz
*
* STM32F411x:
*
* LATENCY | 2.7V - 3.6V | 2.4V - 2.7V | 2.1V - 2.4V | 1.7V - 2.1V
* ------- | ----------- | ----------- | ----------- | -----------
* 0 | 30 MHz | 24 MHz | 18 MHz | 16 MHz
* 1 | 64 MHz | 48 MHz | 36 MHz | 32 MHz
* 2 | 90 MHz | 72 MHz | 54 MHz | 48 MHz
* 3 | 100 MHz | 96 MHz | 72 MHz | 64 MHz
* 4 | | 100 MHz | 90 MHz | 80 MHz
* 5 | | | 100 MHz | 96 MHz
* 6 | | | | 100 MHz
*/
static inline void __setup_flash(void)
{