SPRAD05E August 2024 – October 2025 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM625SIP
The recommendation is to indicate the configured boot mode and the boot mode provisions provided in the block diagram including primary boot and backup boot.
For supported boot mode configurations, see the following FAQ:
The processor family supports multiple peripheral interfaces that support boot. For the available boot mode configurations and supported peripherals, see the device-specific TRM. The processor family supports primary boot mode and an optional backup boot mode configuration. If the primary boot (source) mode fails, the ROM switches on to the backup boot mode.
Boot mode configuration to be used (by the ROM code) during boot are set by the boot mode configuration (pullup or pulldown) resistors connected to the processor boot mode inputs directly (or through external buffers). The BOOTMODE [15:0] pin configurations (level) are latched into the Device Status register CTRLMMR_MAIN_DEVSTAT[15:0] as the processor comes out of cold reset, sampled after MCU_PORz input deassertion (rising edge of PORz_OUT output (buffered output of MCU_PORz input)). The boot mode configuration inputs are recommended to be stable before releasing (deassertion) the MCU_PORz input.
Processor boot mode can be configured using discrete (parallel pull) resistors for the below boot configuration (functionality):
PLL Config (Configuration): BOOTMODE [02:00] – PLL config pins are used to indicate the system clock (PLL reference clock selection) frequency (MCU_OSC0_XI/XO) to ROM code for PLL configuration
For supported crystal frequency see the processor-specific data sheet. Configure the boot mode to match the supported crystal or clock frequency. Wrong clock frequency configuration affects the processor performance including resetting of the board.
Primary Boot Mode: BOOTMODE [06:03] – The boot mode pins are used to configure the required primary boot mode, i.e, the peripheral/memory to boot from
Primary Boot Mode Config: BOOTMODE [09:07] – The boot mode configuration pins support optional configurations for primary boot and are used in conjunction with the primary boot mode selection pins
Backup Boot Mode: BOOTMODE [12:10] – The boot mode pins are used to configure the required backup boot mode, i.e., the peripheral/memory to boot from, in case primary boot fails
Backup Boot Mode Config: BOOTMODE [13] – The boot mode pin provides additional configuration options (optional - depends on the selected backup boot mode pins)
Reserved: BOOTMODE [15:14] – Reserved pins (The recommendation is to not leave the reserved pins unconnected)
Key considerations when configuring boot mode:
For information related to supported boot modes, see the Initialization chapter of the device-specific TRM and device-specific silicon errata.
Custom board designers are responsible for providing provision to set the required boot mode configuration (using pullups or pulldowns, or optionally using jumpers/switches (with provision for external ESD protection when set in uncontrolled ESD environment)). The recommendation is to provide provision for pullup and pulldown for the boot mode input pins that have configuration capability for increase design flexibility. Shorting of multiple boot mode input pins together, leaving any of the boot mode input pins unconnected or connecting the boot mode inputs directly to supply or ground is not recommended or allowed.
The recommendation is to connect the processor boot mode input pins (configured for alternate function) to the alternate function through a 0Ω series resistor. Series resistor can be used to isolate the alternate function during testing.
For implementing the boot mode, see the following FAQs: