MC68711E20CFNE3 Datasheet, PDF (31/242 Pages) –

Memory Map
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.
$0000
EXT
$1000
0000
512 BYTES RAM
EXT
01FF
1000 _{64-BYTE REGISTER BLOCK}
103F
$B600
EXT
$D000
EXT
BF00 ^BOOT
ROM
BFC0 _{SPECIAL MODES}
INTERRUPT
BFFF
BFFF ^VECTORS
$FFFF
EXPANDED
FFC0
FFFF
NORMAL
MODES
INTERRUPT
VECTORS
BOOTSTRAP
SPECIAL
TEST
Figure 2-2. Memory Map for MC68HC11E0
M68HC11E Family Data Sheet, Rev. 5.1
Freescale Semiconductor
31