topic Re: Why is the recommended value for csHoldTime and csSetupTime 0x3? in i.MX RT Crossover MCUs

Why is the recommended value for csHoldTime and csSetupTime 0x3?

imxrtuser — Fri, 03 Apr 2020 06:32:19 GMT

Hello,

the recommended value for csHoldTime and csSetupTime is 0x3.

Why is the recommended value for csHoldTime and csSetupTime 0x3? Is it okay to set it to 0x1 if my used flash device is fast enough or will the FlexSPI peripheral have problems with a value of 0x1?

Kind regards,

Stefan

Re: Why is the recommended value for csHoldTime and csSetupTime 0x3?

kerryzhou — Tue, 07 Apr 2020 06:23:14 GMT

Hi Stefan Mitterhauser,

The csHoldTime and csSetupTime, you need to check your external flash datasheet, normally, it defines the related min time:

So, when you configure the flexSPI configuration block, you need to use your flexSPI clock to calculate your CS setup time and the hold time, make sure the time is larger than your flash datasheet defined smallest time.

Wish it helps you!

Kerry

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Re: Why is the recommended value for csHoldTime and csSetupTime 0x3?

imxrtuser — Tue, 07 Apr 2020 07:02:24 GMT

Hi Kerry,

thank you for your answer. I did take the values from the data sheet of our flash device, but it still would be good to know why NXP recommends a value of 3 in the reference manual - there must be a reason for that right?

Kind regards,

Stefan

Re: Why is the recommended value for csHoldTime and csSetupTime 0x3?

kerryzhou — Tue, 07 Apr 2020 07:23:18 GMT

Hi Stefan Mitterhauser,

My own opinion is 0x03 value may meet a lot of the external flash csHoldTime and csSetupTime requirement.

So, if your external flash also can use 0X03, you can use it, but if you still want to change the data, eg, 0X01, you can check your datasheet, if it meets your requirement, then try 0X01 to test it, I think it's Ok, it is not fixed to 0X03.

Wish it helps you!

Kerry

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Re: Why is the recommended value for csHoldTime and csSetupTime 0x3?

imxrtuser — Tue, 07 Apr 2020 09:10:47 GMT

Okay, thank you!