# Frequency calculator formula of QSPI DDR read

## Frequency calculator formula of QSPI DDR read

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Contributor IV

Hello community,

On NOTE of Figure 32. QuadSPI Input/Read timing (DDR mode) in datasheet VF3xxR, VF5xxR, Rev. 8, 01/2018, it say that

• The numbers are for a setting of 0x1 in register QuadSPI_SMPR[DDRSMP]
• Read frequency calculations should be: Tck/2 > (flash access time) + Setup (Tis) - (QuadSPI_SMPR[DDRSMP])x Tck/4
• Frequency calculator guideline (Max read frequency): Tck/2 > (Flash access time)max +  (Tis)max - (QuadSPI_SMPR[DDRSMP]) x Tck/4
• Hold timing: flash_access (min) + flash_data_valid (min) > Tck/2 + HOLD(Tih) +  (QuadSPI_SMPR[DDRSMP])Tck/4

But Figure 30-422. DDR sampling edges of Vybrid Reference Manual, Rev. 5, 06/2014 or

Figure 10-25. 4x sampling edges in DDR mode of VFxxx Controller Reference Manual, Rev. 8, 11/2015,

It seems that step of QuadSPI_SMPR[DDRSMP] is Tck/8

• The numbers are for a setting of 0x1 in register QuadSPI_SMPR[DDRSMP]
• Read frequency calculations should be: Tck/2 > (flash access time) + Setup (Tis) - (QuadSPI_SMPR[DDRSMP])x Tck/8
• Frequency calculator guideline (Max read frequency): Tck/2 > (Flash access time)max +  (Tis)max - (QuadSPI_SMPR[DDRSMP]) x Tck/8
• Hold timing: flash_access (min) + flash_data_valid (min) > Tck/2 + HOLD(Tih) +  (QuadSPI_SMPR[DDRSMP])Tck/8

How do you think about time period of QuadSPI_SMPR[DDRSMP]?

Best regards,

Ishii.

• ### VF5xxR

1 解答
3,520 次查看
NXP Employee

You are right in that the QuadSPI read sample point fine tune step is Tck/8, not
Tck/4. There is a typo in the Data Sheet document.

Best Regards,
Artur

2 回复数
2,116 次查看
Contributor IV

Hello @Romainers

You are asking us to explain this system.

But your request is too vague and I don't know what you are asking for.

Is your request in this?

1) "this system" mean about NXP community, so please explain the community web site.

2) "this system" mean about Vybrid, so please explain the Vybrid device.

3) "this system" mean about QSPI Flash, so please explain about QSPI Flash.

I think, if you limit the scope of your question a bit more, you can expect a better answer.

Best regards,

Ishii.

3,521 次查看
NXP Employee

You are right in that the QuadSPI read sample point fine tune step is Tck/8, not
Tck/4. There is a typo in the Data Sheet document.

Best Regards,
Artur