IMX7 BOOT_CFG Pins Unused and Relevant to Mode Selected

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IMX7 BOOT_CFG Pins Unused and Relevant to Mode Selected

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davidsabalesky
Contributor I

Documentation is IMX7 Dual Application Processor Reference Manual.

The IMX7 in Boot Internal Mode [1,0] uses Boot_CFG[19:0] pins to determine device selected and associated parameters of device. EFUSES are not blown and reside in their default state.

Consider only two device selections available Boot_CFG[15;12] = 0110 (Serial ROM SPI) or 0001 (SD/eSD/SDXC)

It is understood that what ever device is selected the associated CFG pins are configured for that function of the device, however there are specific pins namely BOOT_CFG[19], CFG[18],CFG[16] that are not listed specific to either device.

How does the IMX7 boot process handle these pins, CFG[19,18,16]?

These three pin are not addressed in Table 6-41 USDHC Boot eFUSE or Table 6-46 Serial ROM Boot eFUSE.

As listed in Table 6-25 Boot eFUSE

CFG[19] is the Infinite Loop enable at start of boot ROM, default state 0.

CFG[18] is BT_FREQ selection.

CFG[16] is BT_MMU_DISABLE and is either MMU....cache...disable or SPI recovery. This may be an error as listed.

When using GPIO state for CFG, are these three pins utilized?

I assume that when a particular device is selected via CFG[15:12], unused CFG pins are IGNORED if not relevant to the device. However these three pins CGF[19], CFG[18], and CFG [16] are not clearly defined as to whether the boot will use the GPIO values for CFG setting.

If any person knows the definitive answer please respond quickly since I am in the final design stages and may have to alter the PCB design to resolve any conflicts.

Thanks,

David

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igorpadykov
NXP Employee
NXP Employee

Hi David

you are right: as listed in Table 6-25 Boot eFUSE

CFG[19] is the Infinite Loop enable at start of boot ROM, default state 0.

CFG[18] is BT_FREQ selection.

CFG[16] is BT_MMU_DISABLE is MMU/cache disable

SPI recovery is BOOT_CFG[17] as listed in Table 6-47. Serial ROM boot eFUSE descriptions

CFG[19,18,16] are used in all boot modes.

>When using GPIO state for CFG, are these three pins utilized?

yes

Best regards
igor
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