
MOTOROLA
3-2
MC68HC11P2
OPERATING MODES AND ON-CHIP MEMORY
3
3.1.3
Special test mode
Special test, a variation of the expanded mode, is primarily used during Motorola’s internal
production testing; however, it is accessible for programming the CONFIG register, programming
calibration data into EEPROM, and supporting emulation and debugging during development.
3.1.4
Special bootstrap mode
When the MCU is reset in special bootstrap mode, a small on-chip ROM is enabled at address
$BE40–$BFFF. The ROM contains a reset vector and a bootloader program. The MCU fetches the
reset vector, then executes the bootloader.
For normal use of the bootloader program, send a synchronization byte $FF to the SCI receiver
at either E clock
÷256, or E clock ÷1664 (7812 or 1200 baud respectively, for an E clock of 2MHz).
Then download up to 1024 bytes of program data (which is put into RAM starting at $0080). These
characters are echoed through the transmitter. The bootloader program ends the download after
a timeout of four character times or 1024 bytes. When loading is complete, the program jumps to
location $0080 and begins executing the code. Use of an external pull-up resistor is required when
using the SCI transmitter pin (TXD) because port D pins are congured for wired-OR operation by
the bootloader. In bootstrap mode, the interrupt vectors point to RAM. This allows the use of
interrupts through a jump table.
Further baud rate options are available on the MC68HC11P2 by using a different value for the
synchronization byte, as shown in
Table 3-1. Refer also to Motorola application note
AN1060,
M68HC11 Bootstrap Mode (the bootloader mode is similar to that used on the MC68HC11K4).
Table 3-1 Example bootloader baud rates
Sync.
byte
Timeout
delay
Baud rates for an E clock of:
2.00MHz 2.10MHz 3.00MHz 3.15MHz 4.00MHz
$FF
4 char.
7812
8192
11718
12288
15624
$FF
4
1200
1260
1800
1890
2400
$F0
4.9
9600
10080
14400
15120
19200
$FD
17.3
5208
5461
7812
8192
10416
$FD
13
3906
4096
5859
6144
7812