i.MX6 eCSPI clock.

[satoshishimoda]

Hi community,

Our partner have a simple question about i.MX6 eCSPI spec.

Please see Table 53 and 54 in IMX6SDLCEC Rev.3.

It says as the following image.

[Q]

We want to know the meaning of "Read" and ""Write".

Which is correct?

A. Read = Read cycle, Write = Write cycle

B. Read = Input to i.MX6, Write = Output from i.MX6

Best Regards,

Satoshi Shimoda

[Yuri · Accepted solution]

The Read means read cycle (i.MX6 input ) ;
the Write means write cycle (i.MX6 output).

Have a great day,
Yuri

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[satoshishimoda]

Hi Yuri,

Sorry, my question was not enough.

In write sequence, yes i.MX6 output = write since i.MX6 does not receive any data on MISO.

On the other hand, In read sequence, i.MX6 behaves as below.

Output instruction from MOSI -> output address from MOSI -> input data to MISO

In this case, clock cycle is not changed both output from MOSI and input to MISO, and its minimum cycle time is 43 ns even though this sequence includes both output and input.

So "The Read means read cycle (i.MX6 input )".

Is this correct?

Best Regards,

Satoshi Shimoda

[Yuri]

   Generaly You are right, SPI interface is bidirectional, assuming the same clock for reading and
writing (both are done simultaneosly). Sometimes SPI can be used as unidirectional, say it is
important to write data to a DAC, but it is not important to get DAC replies. For such deivices
one can configure i.MX6 for maximal frequency of write op (which differs from maximal freqiency
of read op). 

~Yuri.

[satoshishimoda]

Dear Yuri,

OK, I understood.

By the way, I found the other description about eCSPI speed.

Please see Table 3 in IMX6SDLCEC (Rev.3).

It says "Full-duplex enhanced Synchronous Serial Interface, with data rate up to 52 Mbit/s.".

This is lower than the spec "15 ns for Write" (60MHz) that we talked in this post.

Which is correct spec?

Best Regards,

Satoshi Shimoda

[Yuri]

The datasheet contains the recent checked specs - so, please use the Datasheet.

~Yuri.

[satoshishimoda]

The both data (15 ns & 52 Mbit/s) are written in datasheet.

Did you said 52 Mbit/s as "Datasheet"?

[Yuri]

The  tables 53 and 54 in IMX6SDLCEC Rev. 3 are correct.

~Yuri.