Embedian, Inc.
155
SMARC-iMX8MM Computer on Module User’s Manual
v. 1.2
4.2.4.
Special
Control
Signals
(TEST#)
SMARC
‐
iMX8MM
does
not
support
to
boot
up
from
SPI
NOR
flash.
SMARC
‐
iMX8MM
module
boots
up
from
the
onboard
eMMC
Flash
first.
The
firmware
in
the
eMMC
flash
will
read
the
BOOT_SEL
configuration
and
decides
where
to
load
the
u
‐
boot.
In
some
situations
like
the
firmware
in
eMMC
flash
needed
to
be
upgrade/restore
or
at
factory
default
where
the
firmware
in
eMMC
flash
is
empty
or
at
development
stage
that
the
firmware
in
eMMC
needs
to
be
modified,
users
will
need
an
alternative
way
to
boot
up
from
SD
card
first.
The
TEST#
pin
serves
as
this
purpose.
The
TEST#
pin
is
pulled
high
on
module.
If
carrier
board
leaves
this
pin
floating
or
pulls
high,
the
module
will
boot
up
from
on
‐
module
eMMC
.
If
carrier
board
pulls
this
pin
to
GND
,
the
module
will
boot
up
from
SD
card
first.
The
first
stage
bootloader
in
i.MX8M
Mini
CPU
ROM
codes
will
load
the
2
nd
stage
bootloader
based
on
the
setting
of
this
#TEST
pin
(
S157
).
