Correct flash wait state settings (doc vs. CMSIS)

Discussion around product based on ARM Cortex M3 core.

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FocusPaul
Posts: 29
Joined: Thu Mar 29, 2012 5:19 pm

Correct flash wait state settings (doc vs. CMSIS)

Thu Oct 16, 2014 8:00 am

Hello!

I'm trying to find out the correct flash wait state settings for my clock (72 MHz) and VDDCORE (1.8 V) setting.

It seems that the wait state values differ between those listed in CMSIS definitions and those in Atmel documentation.

For example, at 1.65 V:

CMSIS (https://github.com/synthetos/ICEtest/bl ... /sam3x4e.h)

Code: Select all

/* Embedded Flash Read Wait State (VDDCORE set at 1.65V) */
#define CHIP_FREQ_FWS_0 (22500000UL) /**< \brief Maximum operating frequency when FWS is 0 */
#define CHIP_FREQ_FWS_1 (34000000UL) /**< \brief Maximum operating frequency when FWS is 1 */
#define CHIP_FREQ_FWS_2 (53000000UL) /**< \brief Maximum operating frequency when FWS is 2 */
#define CHIP_FREQ_FWS_3 (78000000UL) /**< \brief Maximum operating frequency when FWS is 3 */
Official documentation (http://www.atmel.com/images/doc11057.pdf), table 46-59 on page 1443 of 1467:

Embedded Flash Wait State VDDCORE set at 1.62V
FWS Maximum Operating Frequency (MHz)
0 -> 17
1 -> 45
2 -> 58
3 -> 70
4 -> 78


Is it safe to just take those values for 1.80 V from the documentation?

Thank you for reading,
Paule
Bogdancev
Posts: 9
Joined: Sun Jul 13, 2014 3:13 pm

Re: Correct flash wait state settings (doc vs. CMSIS)

Fri Oct 17, 2014 8:06 am

You can always use 4 to be sure.
Did you try?
nutsnbolts
Posts: 31
Joined: Mon Aug 25, 2014 11:20 pm

Re: Correct flash wait state settings (doc vs. CMSIS)

Tue Oct 21, 2014 6:54 pm

See doc11057 (as above), page 311:
• FWS: Flash Wait State This field defines the number of wait states for read and write operations: Number of cycles for Read/Write operations = FWS+1
So, for 4 wait cycles, program with 3 (3+1...) Regards, Mike
FocusPaul
Posts: 29
Joined: Thu Mar 29, 2012 5:19 pm

Re: Correct flash wait state settings (doc vs. CMSIS)

Wed Oct 22, 2014 6:59 am

Please do not understand my answer as rude. I do not intend to.

There has no reply in this thread yet, which answered the initial question.

Going with the highest wait state setting is like driving a car on lowest gear and lowest speed because you do not know how to drive a car. The intention of my question was about the manufacturer-defined top speed, not the safest possible speed.

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