XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 80

• Manufacturer Part Number: XC912BC32CFU8
• Description: M68HC12B Family Data Sheet
• Manufacturer: Motorola Semiconductor Products

Operating Modes and Resource Mapping
5.3 Internal Resource Mapping
5.4 Mode and Resource Mapping Registers
Data Sheet
80
BDM allows read and write access to internal memory-mapped registers and RAM
and read access to EEPROM, FLASH EEPROM, or ROM without interrupting the
application code executing in the CPU. This non-intrusive mode uses dead bus
cycles to access the memory and in most cases will remain cycle deterministic.
Refer to
The internal register block, RAM, FLASH EEPROM/ROM, and EEPROM have
default locations within the 64-Kbyte standard address space but may be
reassigned to other locations during program execution by setting bits in mapping
registers INITRG, INITRM, and INITEE. During normal operating modes, these
registers can be written once. It is advisable to explicitly establish these resource
locations during the initialization phase of program execution, even if default values
are chosen, to protect the registers from inadvertent modification later.
Writes to the mapping registers go into effect between the cycle that follows the
write and the cycle after that. To assure that there are no unintended operations,
a write to one of these registers should be followed with a no operation (NOP)
instruction.
If conflicts occur when mapping resources, the register block will take precedence
over the other resources; RAM, FLASH EEPROM/ROM, or EEPROM addresses
occupied by the register block will not be available for storage. When active, BDM
ROM takes precedence over other resources, although a conflict between BDM
ROM and register space is not possible.
precedence.
In expanded modes, all address space not utilized by internal resources is by
default external memory.
This section describes the mode and resource mapping registers.
18.3 Background Debug Mode (BDM)
Operating Modes and Resource Mapping
Precedence
1
2
3
4
5
6
Table 5-2. Mapping Precedence
Table 5-2
FLASH EEPROM/ROM
BDM ROM (if active)
External memory
Register space
for more details.
Resource
EEPROM
shows resource mapping
RAM
M68HC12B Family — Rev. 8.0
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