17.3 Hardware and Software Constraints

  • SAM-BA Boot uses the first 2048 bytes of the SRAM for variables and stacks. The remaining available bytes can be used for the user code.
  • USB requirements:
    • External crystal or external clock (see Note below) with frequency of 12 MHz or 16 MHz
    Note: Must be 2500 ppm and VDDIO square wave signal.
  • UART0 requirements:
    • None. If accurate external clock source is not available, the internal 12 MHz RC meets RS-232 standards at room temperature.
    Table 17-1. Pins Driven during Boot Program Execution
    Peripheral Pin PIO Line
    UART0 URXD0 PA9
    UART0 UTXD0 PA10