AI 生成的摘要: The DA1458x boots from external serial devices when the OTP memory is unprogrammed, entering Development Mode to allow code download via UART, SPI, or I2C interfaces. The boot sequence prioritizes SPI Master, SPI Slave, UART, and I2C communication through specific pin assignments on port P0. The boot code attempts communication in a defined order and retries multiple times before entering an infinite loop with JTAG enabled if no device responds. The document details pin configurations, boot protocols, timing, and communication sequences necessary for establishing external boot communication.