
Application Note
AN1060 — Rev. 1.0
210
MOTOROLA
Topics discussed in this application note include:
Basic operation of the M68HC11 bootstrap mode 
General discussion of bootstrap mode uses 
Detailed explanation of on-chip bootstrap logic 
Detailed explanation of bootstrap firmware 
Bootstrap firmware vs. EEPROM security 
Incorporating the bootstrap mode into a system 
Driving bootstrap mode from another M68HC11 
Driving bootstrap mode from a personal computer 
Common bootstrap mode problems 
Variations for specific versions of M68HC11 
Commented listings for selected M68HC11 bootstrap ROMs 
Basic Bootstrap Mode
This section describes only basic functions of the bootstrap mode. Other 
functions of the bootstrap mode are described in detail in the remainder 
of this application note. 
When an M68HC11 is reset in bootstrap mode, the reset vector is 
fetched from a small internal read-only memory (ROM) called the 
bootstrap ROM or boot ROM. The firmware program in this boot ROM 
then controls the bootloading process, in this manner:
First, the on-chip SCI (serial communications interface) is 
initialized. The first character received ($FF) determines which of 
two possible baud rates should be used for the remaining 
characters in the download operation. 
Next, a binary program is received by the SCI system and is stored 
in RAM. 
Finally, a jump instruction is executed to pass control from the 
bootloader firmware to the user’s loaded program.
F
Freescale Semiconductor, Inc.
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