The I/O buffers for the MIO pins used to interface to the boot device are configured by the RCU BootROM with these attributes:
- Default drive strength (8 mA)
- Default slew rate (slow)
- Default weak pull-ups (enabled)
- Enables the Schmitt trigger
- Disables the 3-state override
If a secure lockdown occurs during boot, the BootROM sets the PMC_GLOBAL.TRISTATE_OVERRIDE register to force all I/Os into a tristate mode. This register is then reserved for use by the PLM firmware.