Specifications

MCU slave software
Developer’s Serial Bootloader, Rev. 13
Freescale Semiconductor 41
The on-chip FLASH programming routines simplify the bootloader and improve memory usage. The
communication between the MCU and PC uses a Standard Serial Channel (SCI).
The following flowchart shows the basic principle of the bootloading algorithm:
Figure 26. MC68HC908KX bootloader flowchart
RESET
SRSR RESET
SOURCE TEST
MCU CONFIG
ICG, SCI INIT
WAIT FOR COMMAND
SEND IDENT DATA
RECEIVE ADDRESS
RECEIVE ADDRESS
RECEIVE LENGTH
RECEIVE DATA
CALL WRITE
ROUTINE IN ROM
CALL ERASE
ROUTINE IN ROM
RECEIVE ADDRESS
RECEIVE LENGTH
SEND DATA
SEND ACK
EXECUTE ILLEGAL
OPERATION
SEND ACK AND
WAIT FOR ANSWER
YES
YES
USER CODE
START
POR CAUSED RESET
DISABLE SCI
MEASURE BREAK
WAIT FOR HI-LO EDGE
TRIM ICG, ENABLE SCI
IDENT? ERASE? WRITE? READ? QUIT?
YES YES YES
YES
NO NO NO NO
NO
1
2
2
1
2
2
2
TIMEOUT EXPIRED
NO
NOT POR
?