SPI timing Lead/Lag times in iMX8 datasheet

[YukioOyama]

Hi all,

In i.MX 8QuadMax Industrial Applications Processors datasheet,

(Document Number: IMX8QMIEC Rev. 1, 04/2022)

In the table60, "SPIx_CSy Lead Time" and "SPIx_CSy Lag Time".
FCLK_PERIOD are divided by the PRESCALE value, but I think it is correct that FCLK_PERIOD should be multiplied by the PRESCALE value.
If the FCLK_PERIOD is divided by the PRESCALE value, the FCLK_PERIOD will be shorter. The FCLK frequency will be very high.

Am I wrong? Or has an errata been issued?

Best Regards,

Yukio Oyama

[AldoG]

Hello,

I think that it may be confusing, since the Lead and Lag time needs to be tiny, it is in ns. So it is correct to be divided by the PRESCALE.

At the same time FCLK frequency is in MHz

Best regards,
Aldo.

[YukioOyama]

Hello Aldo-san,

Thanks for the support.
Could you please tell me with a concrete example.

When FCLK=120MHz, FCLK_PERIOD is 8.3[ns].
Assuming PRESCALE=3, FCLK_PERIOD/2^PRESCALE=1.04[ns].

Assuming PCSSCK=0, the Lead time is
FCLK_PERIOD(PCSSCK+1)/2^PRESCALE-3[ns].
= -1.96[ns].
This is a negative value, is it correct?

I may have misunderstood some parameters. Are there any unusual values I have assumed?

Best Regards,

Yukio Oyama

[AldoG]

Hi,

Well it is incorrect, please note that it is + not -, so in your same example:

When FCLK=120MHz, FCLK_PERIOD is 8.3[ns].

Assuming PRESCALE=3, FCLK_PERIOD/2^PRESCALE=1.04[ns].

Assuming PCSSCK=0, the Lead time is

FCLK_PERIOD(PCSSCK+1)/2^PRESCALE+3[ns].

= 4.04[ns].

Best regards,
Aldo.

[YukioOyama]

Hi Aldo-san,

In my first question, I made a mistake in the document to which I should have referred. The correct reference was Table 59 and the Lead time.

It is "+3" at 40 MHz (1.8 V I/O) but "-3" at 60 MHz I/F.
And when calculated, it is negative.

I did not check enough when I posted my question. My apologies for confusing you.

Best Regards,

Yukio Oyama

[AldoG]

Hello Yukio Oyama-San,

I think this may be a typo in the datasheet I'll check with team if this is the case and update as soon as possible.

Best regards,
Aldo.

[AldoG · Accepted solution]

Hello @YukioOyama-san,

I have confirmation from team that this is a typo, it is now reported to documentation team, thank you for spoting it.

Best regards,
Aldo.

[YukioOyama]

Hello Aldo-san,

I understand that is a typo.
I thank you for your faithful support.

Best Regards,

Yukio Oyama