2.5.1.4.2 Using a Boot Configuration Packet
Several boot configuration parameters can be customized by writing a Boot Configuration Packet in the OTP User area:
- IO configuration of boot memories (see Hardware and Software Constraints for a description of the IOs)
- Boot sequence
- UART port for the ROM code console
- Monitor disable
See Boot Configuration Packet for a detailed description of all the fields in this packet.
Out of factory, the OTP User area is empty and thus contains no Boot Configuration Packet.
OTP Emulation Mode
During a prototyping phase or for test purposes, it is possible to use the OTP Emulation mode. In this mode, the OTP matrix is replaced by an internal SRAM1. Once the Emulation mode is enabled, every OTP packet read and write is done in the internal SRAM1 instead of the OTP matrix. To instruct the ROM code to use this feature, set the bit EMUL_EN in the Boot Sequence Controller Configuration register (BSC_CR).
When using the emulated OTP, the user can test several boot configuration options, including the Secure Boot mode, without programming the OTP.
- The emulation SRAM is not backed up. After a power off/power on sequence, the configuration and content are lost.
- Once a packet is written in the OTP matrix, the OTP Emulation mode is no more available. Any instruction from the user to enable this mode in BSC_CR will fail, and packets will be read or written in the OTP memory.