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6.8 SW1: SPI Boot Device Selection
The ETX-BT supports a form of fail-safe BIOS. In the case that the primary BIOS is
corrupted and the BIOS POST takes longer than normal, the system’s POST watchdog will
time out and the system will reset with the secondary SPI Flash BIOS assigned as
primary.
For information on monitoring and operation of the fail-safe BIOS, please refer to SEMA
documentation.
The SW1 switch allows users to change the boot behavior of the module. It sets the
module to either fail safe-mode, or assigns SPI0 or SPI1 as the boot BIOS while providing
access to the other SPI flash device.
Switch Settings
SPI Function
Pin 1
Pin 2
Comment
SPI0 fails-safe
mode
OFF ON
Boot from SPI0, SPI1 is secondary SPI flash
(default)
SPI1 boot
OFF
OFF
Boot from SPI1, no fail-safe, SPI0 not
accessible
SPI0 boot
ON
ON
Boot from SPI0, no fail-safe, SPI1 not
accessible
SPI1 boot
ON
OFF
Boot from SPI1, no fail-safe, SPI0 not
accessible
