Unable to boot Vybrid using QSPI1 in RCON boot mode

richarddonkin · ‎06-27-2014

We have a custom board which uses the QSPI interface with a Spansion S25FL128S flash chip for booting.

I was unable to boot the device when BOOTMOD was [1,0] for RCON boot mode.

richarddonkin · ‎06-27-2014

The RCON31 configuration pin causes the boot ROM to enter an infinite loop if it is pulled high (by design).

Unfortunately, the RCON31 pin is also the QSPI1 flash's HOLD pin, which the flash chip pulls high.

Therefore, you cannot boot in RCON mode using the QSPI1 interface.

I was able to work around it by programming the fuses, including BT_FUSE_SEL, and booting in "Boot From Fuses" mode. So, we are able to continue now. However, it is very important to be sure that the boot image is correct before flashing it and setting the fuses. If the boot image has a memory access bug, the Vybrid may hang in a way which makes it impossible to access even using JTAG.

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richarddonkin · ‎06-27-2014

The RCON31 configuration pin causes the boot ROM to enter an infinite loop if it is pulled high (by design).

Unfortunately, the RCON31 pin is also the QSPI1 flash's HOLD pin, which the flash chip pulls high.

Therefore, you cannot boot in RCON mode using the QSPI1 interface.

I was able to work around it by programming the fuses, including BT_FUSE_SEL, and booting in "Boot From Fuses" mode. So, we are able to continue now. However, it is very important to be sure that the boot image is correct before flashing it and setting the fuses. If the boot image has a memory access bug, the Vybrid may hang in a way which makes it impossible to access even using JTAG.