Technical Data
MC68HC11E Family
—
Rev. 4
68
Operating Modes and On-Chip Memory
MOTOROLA
Operating Modes and On-Chip Memory
Figure 4-1. Address/Data Demultiplexing
4.3.4 Bootstrap Mode
When the MCU is reset in special bootstrap mode, a small on-chip
read-only memory (ROM) is enabled at address $BF00
–
$BFFF. The
ROM contains a bootloader program and a special set of interrupt and
reset vectors. The MCU fetches the reset vector, then executes the
bootloader.
Bootstrap mode is a special variation of the single-chip mode. Bootstrap
mode allows special-purpose programs to be entered into internal
random-access memory (RAM). When bootstrap mode is selected at
reset, a small bootstrap ROM becomes present in the memory map.
Reset and interrupt vectors are located in this ROM at $BFC0
–
$BFFF.
The bootstrap ROM contains a small program which initializes the serial
communications interface (SCI) and allows the user to download a
program into on-chip RAM. The size of the downloaded program can be
as large as the size of the on-chip RAM. After a 4-character delay, or
after receiving the character for the highest address in RAM, control
HC373
D1
MCU
ADDR13
ADDR12
ADDR11
ADDR10
ADDR9
ADDR8
ADDR14
ADDR5
ADDR4
ADDR3
ADDR2
ADDR1
ADDR0
ADDR6
DATA5
DATA4
DATA3
DATA2
DATA1
DATA0
DATA6
D2
D3
D4
D5
D6
D7
D8
LE
Q3
Q4
Q5
Q6
Q7
Q8
OE
Q2
PC5
PC4
PC3
PC2
PC1
PC0
AS
PC6
PB5
PB4
PB3
PB2
PB1
PB0
PB6
R/W
E
WE
OE