AM4372: QSPI boot's dummy byte

Sh.Sasaki

Guru 13625 points

Part Number: AM4372

Hi all,

When AM4372 performs QSPI boot, how many bytes is the dummy data?

Best regards,

Sasaki

over 7 years ago

0 Biser Gatchev-XID over 7 years ago

TI__Guru**** 393215 points

Hi,

Please read section 5.2.6.7 in the AM437x TRM.

0 Sh.Sasaki over 7 years ago in reply to Biser Gatchev-XID

Guru 13625 points

Hi-Biser-san,

Thank you for your support.
I read section 5.2.6.7, but I could not find a description about the dummy. Since there is no description about the dummy,
can I think that the dummy is 0?

Best regards,
Sasaki

0 Biser Gatchev-XID over 7 years ago in reply to Sh.Sasaki

TI__Guru**** 393215 points

From section 5.2.6.7.2:

"There is no specific device identification routine executed by the ROM code to identify whether a boot device is preset. If no QSPI device is present, the QSPI read will return only 0xFFFFFFFF and the QSPI boot will be treated as failed."

This means that the ROM code reads out and check the first 4 bytes initially.

0 Sh.Sasaki over 7 years ago in reply to Biser Gatchev-XID

Guru 13625 points

Hi Biser-san,

Thank you for your reply.

But I can't undaerstand it.

TMDXIDK437X's QSPI FLASH(MX66L51235) has the following waveform when looking at the MX66L51235's data sheet.

The dummy read of this waveform is written as 8 bits by default.

I think that the AM437x will read the QSPI after this dummy cycles.
I want to know the number of dummy cycles.

Best reagrds,

Sasaki

0 melissaw over 7 years ago in reply to Sh.Sasaki

TI__Genius 16030 points

Hi Sasaki-san,

The number of dummy cycles is not important, as long as they’re less than 4 bytes (0xFFFFFFFF).

Regards,
Melissa

0 Sh.Sasaki over 7 years ago in reply to melissaw

Guru 13625 points

Hi Melissa-san,

I apologize for keep asking but I still have something unclear.
I can not understand why they are not important as long as they are less than 4 bytes (0xFFFFFFFF).
Plsease let me know the reason.

Best regards,
Sasaki

0 melissaw over 7 years ago in reply to Sh.Sasaki

TI__Genius 16030 points

Sasaki-san,

I was mistaken. AM437x QSPI boot uses 1 dummy byte.

Sorry for the confusion.

Regards,
Melissa

0 Sh.Sasaki over 7 years ago in reply to melissaw

Guru 13625 points

Hi Melissa-san,

Thank you for your support!

I got it.

Best regards,

Sasaki

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AM4372: QSPI boot's dummy byte