PXD20RM Datasheet, PDF (186/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

START_ADDRESS[31:16]
START_ADDRESS[15:0]
VLE
CODE_LENGTH[30:16]
CODE_LENGTH[15:0]
Figure 6-6. Start address, VLE bit and download size in bytes
6.5.4.7 Download data
Each byte of data received is stored into device’s SRAM, starting from the address specified in the
previous protocol step.
The address increments until the number of bytes of data received matches the number of bytes specified
in the previous protocol step.
Since the SRAM is protected by 32-bit wide Error Correction Code (ECC), BAM always writes bytes into
SRAM grouped into 32-bit words. If the last byte received does not fall onto a 32-bit boundary, BAM fills
it with 0 bytes.
Then a “dummy” word (0x0000_0000) is written to avoid ECC error during core prefetch.
6.5.4.8 Execute code
The BAM program waits for the last echo message transmission being completed.
Then it restores the initial MCU configuration and jumps to the loaded code at Start Address which was
received in step 2 of the protocol.
At this point BAM has finished its tasks and MCU is controlled by new code executing from SRAM.
6.5.5 Boot from UART
6.5.5.1 Configuration
Boot from UART protocol is implemented by the LINFlex 0 module. The pins used are:
• LINFlex_TX corresponds to pin PB[2]
• LINFlex_RX corresponds to pin PB[3].
The system clock is driven by an external oscillator.
6-10
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
Freescale Semiconductor