MC68HC11KW1 Datasheet, PDF (46/238 Pages) Motorola, Inc – High-density complementary metal oxide semiconductor HCMOS) microcontroller unit

For information about the four programmable chip selects available in expanded modes, refer to
Section 4.5. A security feature can protect EEPROM data when in expanded mode (see
Section 4.6.3).
4.1.3 Special test mode
Special test, a variation of the expanded mode, is used during Motorola’s internal production
4
testing, and is not intended or recommended for any other purpose. Its specification is subject to
change without notice.
4.1.4 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 (15624 or 2400 baud respectively, for an E clock of
4 MHz). Then download up to 768 bytes of program data (which is put into RAM starting at
$00A0). These characters are echoed through the transmitter. The bootloader program ends the
download after a timeout of four character times or 768 bytes. When loading is complete, the
program jumps to location $00A0 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 configured
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 MC68HC11KW1 by using a different value for the
synchronization byte, as shown in Table 4-1.
Refer also to Motorola application note AN1060, M68HC11 Bootstrap Mode (the bootloader
mode is similar to that used on the MC68HC11K4).
Table 4-1 Example bootloader baud rates
Sync. byte
$FF
$FF
$F0
$FD
$FD
Timeout delay
4 char.
4
4.9
17.3
13
Baud rates for an E clock of 4.00MHz
15 624
2 400
19 200
10 416
7 812
OPERATING MODES AND ON-CHIP MEMORY
MC68HC11KW1
4-2