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
those customers using security.
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.