# Boot configuration GPIOs
Source: [https://docs.qualcomm.com/doc/80-88500-4/topic/11_Boot_configuration_GPIOs.html](https://docs.qualcomm.com/doc/80-88500-4/topic/11_Boot_configuration_GPIOs.html)
The boot configuration control is implemented based on the input values of the
boot-related GPIOs.
| Boot configuration number | GPIO number | Function | Bit values |
| --- | --- | --- | --- |
| BOOT\_CONFIG\_0 | GPIO\_128 | WDOG disable |
- 1 – Disables Watchdog (WDOG)
- 0 – Enables WDOG
|
| BOOT\_CONFIG\_1 | GPIO\_27 | Fastboot bit 0 | Selects external boot device |
| BOOT\_CONFIG\_2 | GPIO\_47 | Fastboot bit 1 | Selects external boot device |
| BOOT\_CONFIG\_3 | GPIO\_76 | Fastboot bit 2 | Selects external boot device |
| BOOT\_CONFIG\_4 | GPIO\_90 | Fastboot bit 3 | Selects external boot device |
| FORCE\_USB\_BOOT | GPIO\_132 | Force USB Download |
- 0 – Releases USB Download mode
- 1 – Enables USB Download mode
|
| | | | |
| | | | |
| | | | |
BOOT\_CONFIG [4:1] settings determine the external boot devices, as shown in the following figure. FAST\_BOOT fuses (OEM\_CONFIG\_ROW0\_LSB) can also select the same Fastboot options.
Caution:
External pulls or logic high on BOOT\_CONFIG [4:1]
before RESOUT\_N getting asserted high can force the device to boot from an unintended boot
device.
Figure : Fastboot configuration
| | GPIO number | GPIO number | GPIO number | GPIO number | |
| --- | --- | --- | --- | --- | --- |
| FAST\_BOOT GPIO [3:0] | 90 | 76 | 47 | 27 | Boot device |
| 0000 | 0 | 0 | 0 | 0 | Default: UFS0 → SDC2 → USB0 → EDL (USB0) |
| 0001 | 0 | 0 | 0 | 1 | SDC2 → UFS0 → EDL (USB0) |
| 0010 | 0 | 0 | 1 | 0 | SDC2 → EDL (USB0) |
| 0011 | 0 | 0 | 1 | 1 | USB0 → EDL (SDC2 → USB0) |
| 0100 | 0 | 1 | 0 | 0 | QSPI → EDL (SDC2 → USB0) |
| 0101 | 0 | 1 | 0 | 1 | SPI → EDL (SDC2 → USB0) |
| 0110 | 0 | 1 | 1 | 0 | UFS0 → USB0 → EDL (USB0) |
| 0111 | 0 | 1 | 1 | 1 | Same as Fastboot[3:0] = 0000
UFS0 → SDC2 → USB0 → EDL (USB0) |
| Others | Reserved | Reserved | Reserved | Reserved | Reserved |
Note:
- Emergency Download mode (EDL))
- Quad serial peripheral interface (QSPI)
- Secure digital card controller (SDC)
- Serial peripheral interface (SPI)
- Universal flash storage (UFS)
Note:
FASTBOOT[4] fuse in OEM\_CONFIG region of QFPROM does not have a corresponding GPIO.
**Parent Topic:** [Boot](https://docs.qualcomm.com/doc/80-88500-4/topic/8_Boot_.html)
Last Published: Aug 18, 2023
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Configuration data table for boot loader](https://docs.qualcomm.com/bundle/publicresource/80-88500-4/topics/10_Boot_loader_configuration.md) [Next Topic
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