Phytec phyCORE-i.MX 6, Hardware Manual

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phyCORE
®
-i.MX 6 [PCM-058]
28 ©
PHYTEC Messtechnik GmbH 2016 L-808e_2
For serial boot (boot mode = 1) the ROM code polls the communication interface selected,
initiates the download of the code into the internal RAM and triggers its execution from
there. Please refer to the
i.MX 6 Reference Manual for more information.
In boot mode 0 and 2 the ROM code finds the bootstrap in permanent memories such as
NAND-Flash or SD-Cards and executes it. The selection of the boot device and the
configuration of the interface required are accomplished with the help of the eFUSEs
and/or the corresponding GPIO input pins.
6.2 Boot Device Selection and Configuration
In normal operation (boot mode 0, or 2), the boot ROM uses the state of BOOT_MODE and
eFUSEs to determine the boot device.
During development it is advisable to set the boot type to “Internal boot”
(BOOT_MODE[1:0]=10
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to allow choosing and configuring the boot device by using GPIO
pin inputs. The input pins are sampled at boot, and override the values of the
corresponding eFUSEs BOOT_CFGx[7:0], if the BT_FUSE_SEL fuse is not blown.
Table 9 lists the eFUSEs BOOT_CFGx[7:0] and the corresponding input pins.
On the phyCORE-i.MX 6 the GPIOs have 10 kΩ pull-up and pull-down resistors preinstalled
to configure eFUSEs BOOT_CFGx[7:0] in accordance with the module features.
However, the specific boot configuration settings, which are set by the on-board
configuration resistors, can be changed by modifying the resistors on the module or by
connecting a configuration resistor (e.g. 10 kΩ) to the configuration signal. Please
consider that any change of the default BCFG configuration can also influence other boot
modes, which might result in faulty boot behavior.
Caution!
Please make sure that the signals shown in Table 9 are not driven by any device on the
baseboard during reset, to avoid accidental change of the boot configuration.
Because of this, we recommend to boot from eFUSE for volume production and use only
internal boot mode for development process
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.
Please refer to the
i.MX 6 Reference Manual for further information about the eFUSEs and
the impact of the settings at the BCFG pins.
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: For series production Phytec offers to order the phyCORE-i.MX 6 with a custom configuration of the eFUSEs