UART1_RTS_B boot pin configuration

[jacopoagostini]

Hi, 

I have a question about boot mode and pin configuration. Is it correct that when the pin UART1_RTS_B is low the system reboot from SD Card. What about if this pin is high?

[Yuri]

Hello,

  UART1_RTS_B is configured as SD CD_B signal during SD boot :

Table 8-18 (SD/MMC IOMUX Pin Configuration) of the i.MX6 UL RM (Rev. 1, 04/2016).

When internal boot failed, “SD or MMC card will be scanned on uSDHC1. If card is detected

and valid boot image is found in card, then boot image will be loaded then executed. Pad

of SD1_CD is used to detect whether card is inserted” - section 8.12 (SD/MMC Manufacture Mode)

of the i.MX6 UL RM.

  So, the UART1_RTS_B pulled low may cause SD boot, if proper card is inserted to SD1

port, even if the SD1 is not default boot device. If the UART1_RTS_B is pulled high - no SD boot occurs.

Have a great day,
Yuri

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[jacopoagostini]

Thanks for the answer.

What about if I configure a simple GPIO pin for the card detection and so I don't choose one of the possible pin listed in datasheet? Is SD Card detection still possible after a software configuration?

[Yuri]

Hello,

  boot options / pin configurations are provided by boot ROM during  boot.

After that it is possible to reconfigure pins as needed. And, yes,  SD Card detection

still possible after a software configuration (under OS) in Your case.

Regards,

Yuri.

[jacopoagostini]

Ok thanks.

My doubt is mainly about the fact that in the datasheet (table 8-7  i.MX6 UL RM  ) I read that to boot from a specific device (SD, NAND, NOR ecc) you simply configure some GPIO pins and I don't understand how UART1_RTS_B pin is involved in this process. 

Regards,

Jacopo