SPRADO8 March 2025 AM62L
In the EVM, the boot mode pins BOOTMODE[15:12], BOOTMODE[11:00] are asserted through 1x 8-bit and 2x 4-bit isolation buffers. The buffers make sure that the SYSBOOT pulls (boot mode configured using resistors) control the IO level of the signals when the boot mode signals are latched (around the RESETSTATz rising edge) by the processor. Since boot mode signals are used for other functions after processor boot and are connected to attached devices or peripherals. The boot mode configuration resistors are isolated from other connected peripherals so that the other connected peripherals do not conflict with the intended boot mode configuration (IO levels).
The buffers are enabled when RESETSTATz is driven low by the processor. Once RESETSTATz is asserted, the buffer outputs are Hi-Z so the signals are not pulled or influenced by the boot mode resistors.
For optimizing the design (including BOM), the buffers can be optimized or deleted depending on the use case. The boot mode pull resistors value are selectable so that the resistors do not affect the operation of attach devices.