Application Note
AN1060
—
Rev. 1.0
316
MOTOROLA
Boot ROM Variations
Different versions of the M68HC11 have different versions of the
bootstrap ROM program.
Table 3
summarizes the features of the boot
ROMs in 16 members of the M68HC11 Family.
The boot ROMs for the MC68HC11F1, the MC68HC711K4, and the
MC68HC11K4 allow additional choices of baud rates for bootloader
communications. For the three new baud rates, the first character used
to determine the baud rate is not $FF as it was in earlier M68HC11s. The
intercharacter delay that terminates the variable-length download is also
different for these new baud rates.
Table 3
shows the synchronization
characters, delay times, and baud rates as they relate to E-clock
frequency.
Commented Boot ROM Listing
Listing 3. MC68HC711E9 Bootloader ROM
contains a complete
commented listing of the boot ROM program in the MC68HC711E9
version of the M68HC11. Other versions can be found in
Appendix B
of
the
M68HC11 Reference Manual
and in the freeware area of the
Motorola Web site.
Table 3. Bootloader Baud Rates
Sync
Character
Timeout
Delay
Baud Rates at E Clock =
2 MHz 2.1 MHz 3 MHz 3.15 MHz 4 MHz
4.2 MHz
$FF
4 characters
7812
8192
11,718
12,288
15,624
16,838
$FF
4 characters
1200
1260
1800
1890
2400
2520
$F0
4.9 characters
9600
10,080
14,400
15,120
19,200
20,160
$FD
17.3 characters
5208
5461
7812
8192
10,416
10,922
$FD
13 characters
3906
4096
5859
6144
7812
8192