
Application Note
AN1060 — Rev. 1.0
214
MOTOROLA
RBOOT is reset to 1 in bootstrap mode to enable the small boot ROM. 
In the other three modes, RBOOT is reset to 0 to keep the boot ROM out 
of the memory map. While in special test mode, SMOD = 1, which allows 
the RBOOT control bit to be written to 1 by software to enable the boot 
ROM for testing purposes. 
Boot ROM Firmware 
The main program in the boot ROM is the bootloader, which is 
automatically executed as a result of resetting the MCU in bootstrap 
mode. Some newer versions of the M68HC11 Family have additional 
utility programs that can be called from a downloaded program. One 
utility is available to program EPROM or OTP versions of the M68HC11. 
A second utility allows the contents of memory locations to be uploaded 
to a host computer. In the MC68HC711K4 boot ROM, a section of code 
is used by Motorola for stress testing the on-chip EEPROM. These test 
and utility programs are similar to self-test ROM programs in other 
MCUs except that the boot ROM does not use valuable space in the 
normal memory map. 
Bootstrap firmware is also involved in an optional EEPROM security 
function on some versions of the M68HC11. This EEPROM security 
feature prevents a software pirate from seeing what is in the on-chip 
EEPROM. The secured state is invoked by programming the no security 
(NOSEC) EEPROM bit in the CONFIG register. Once this NOSEC bit is 
programmed to 0, the MCU will ignore the mode A pin and always come 
out of reset in normal single-chip mode or special bootstrap mode, 
depending on the state of the mode B pin. Normal single-chip mode is 
the usual way a secured part would be used. Special bootstrap mode is 
used to disengage the security function (only after the contents of 
EEPROM and RAM have been erased). Refer to the 
M68HC11 
Reference Manual
, Motorola document order number M68HC11RM/AD, 
for additional information on the security mode and complete listings of 
the boot ROMs that support the EEPROM security functions. 
F
Freescale Semiconductor, Inc.
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