SLASFB6 December 2025 MSPM33C321A
ADVANCE INFORMATION
The bootstrap loader (BSL) enables configuration of the device as well as programming of the device memory through a UART or I2C serial interface. Access to the device memory and configuration through the BSL is protected by a 256-bit user-defined HASH password, and it is possible to completely disable the BSL in the device configuration, if desired. The BSL is enabled by default from TI to support use of the BSL for production programming.
A minimum of two pins are required to use the BSL: the BSL_UART_RX and BSL_UART_TX signals (for UART), or the BSL_I2C_SCL and BSL_I2C_SDA signals (for I2C) or the BSL_CAN_RX and BSL_CAN_TX signals (for CAN). Additionally, one or two additional pins (BSL_INVOKE and NRST) may be used for controlled invocation of the bootloader by an external host.
If enabled, the BSL may be invoked (started) in the following ways:
| DEVICE SIGNAL | CONNECTION | BSL FUNCTION |
|---|---|---|
| BSL_UART_RX | Required for UART | UART receive signal (RX), an input |
| BSL_UART_TX | Required for UART | UART transmit signal (TX) an output |
| BSL_I2C_SCL | Required for I2C | I2C BSL clock signal (SCL) |
| BSL_I2C_SDA | Required for I2C | I2C BSL data signal (SDA) |
| BSL_CAN_RX | Required for CAN | CAN receive signal (RX), an input |
| BSL_CAN_TX | Required for CAN | CAN receive signal (TX), an output |
| BSL_INVOKE | Optional | Active-high digital input used to start the BSL during boot |
| NRST | Optional | Active-low reset pin used to trigger a reset and subsequent check of the invoke signal (BSL_invoke) |
For a complete description of the BSL functionality and command set, see the MSPM33C3x Bootloader User's Guide.