19.1.5 Standard Monitor
This part of the ROM code is executed when no valid code is found in any external Flash memory during the NVM boot sequence, and if the MON_DIS field is not set to 1 in the Boot Configuration Packet.
The main RC oscillator is still used as the main clock.
To use the USB device interface, an external quartz or accurate clock must be connected to the chip.
In case no external clock source is supplied, the USB interface is not activated and only a UART connection can be used as a monitor.
The monitor steps are:
- Initialize UART and USB.
- Check if USB device enumeration occurred.
- Check if characters are received on the UART.
Once the communication interface is identified, the monitor runs in an infinite loop waiting for different commands as listed in Command List.