
MOTOROLA
2-10
SIGNAL DESCRIPTIONS AND OPERATING MODES
MC68HC11A8
TECHNICAL DATA
2
2.2.4 Additional Boot Loader Program Options
The user may transmit a $55 (only at E clock/16) as the first character rather than the
normal $FF. This will cause the program to jump directly to location $0000, skipping
the download.
The user may tie the receiver to the transmitter (with an external pull-up resistor). This
will cause the program to jump directly to the beginning of EEPROM ($B600). Another
way to cause the program to jump directly to EEPROM is to transmit either a break or
$00 as the first character rather than the normal $FF.
Note that none of these options bypass the security check and so do not compromise
Keep in mind that upon entry to the downloaded program at location $0000, some reg-
isters have been changed from their reset states. The SCI transmitter and receiver are
enabled which cause port D pins 0 and 1 to be dedicated to SCI use. Also port D is
configured for wired-OR operation. It may be necessary for the user to write to the
SCCR2 and SPCR registers to disable the SCI and/or port D wire-OR operation.
2.2.5 Special Test Operating Mode
The test mode is a special operating mode intended primarily for factory testing. This
mode is very similar to the expanded multiplexed operating mode. In special test op-
erating mode, the reset and interrupt vectors are fetched from external memory loca-
tions $BFC0–$BFFF rather than $FFC0–$FFFF. There are no time limits for protection
of the TMSK2, OPTION, and INIT registers, so these registers may be written repeat-
edly. Also a special TEST1 register is enabled which allows several factory test func-
tions to be invoked.
The special test operating mode is not recommended for use by an end user because
of the reduced system security; however, an end user may wish to come out of reset
in special test operating mode. Then, after some initialization, the SMOD and MDA bits
could be rewritten to select a normal operating mode to re-enable the protection fea-
tures.