Memory Map
M68HC11E Family Data Sheet, Rev. 5.1
Freescale Semiconductor
31
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 passes to the loaded program at
$0000. Refer to
Figure 2-2
,
Figure 2-3
,
Figure 2-4
,
Figure 2-5
, and
Figure 2-6
.
Use of an external pullup resistor is required when using the SCI transmitter pin because port D pins are
configured for wired-OR operation by the bootloader. In bootstrap mode, the interrupt vectors are directed
to RAM. This allows the use of interrupts through a jump table. Refer to the application note AN1060
entitled
M68HC11 Bootstrap Mode
, that is included in this data book
.
2.3 Memory Map
The operating mode determines memory mapping and whether external addresses can be accessed.
Refer to
Figure 2-2
,
Figure 2-3
,
Figure 2-4
,
Figure 2-5
, and
Figure 2-6
, which illustrate the memory maps
for each of the three families comprising the M68HC11 E series of MCUs.
Memory locations for on-chip resources are the same for both expanded and single-chip modes. Control
bits in the configuration (CONFIG) register allow EPROM and EEPROM (if present) to be disabled from
the memory map. The RAM is mapped to $0000 after reset. It can be placed at any 4-Kbyte boundary
($x000) by writing an appropriate value to the RAM and I/O map register (INIT). The 64-byte register block
is mapped to $1000 after reset and also can be placed at any 4-Kbyte boundary ($x000) by writing an
appropriate value to the INIT register. If RAM and registers are mapped to the same boundary, the first
64 bytes of RAM will be inaccessible.
Refer to
Figure 2-7
, which details the MCU register and control bit assignments. Reset states shown are
for single-chip mode only.
Figure 2-2. Memory Map for MC68HC11E0
FFC0
FFFF
NORMAL
MODES
INTERRUPT
VECTORS
64-BYTE REGISTER BLOCK
512 BYTES RAM
BOOTSTRAP
SPECIAL
TEST
EXT
0000
1000
103F
BF00
EXPANDED
BFFF
BFC0
BFFF
SPECIAL MODES
INTERRUPT
VECTORS
BOOT
ROM
EXT
EXT
01FF
EXT
$0000
$1000
$B600
$D000
$FFFF