Datasheet

Resource Mapping
MC9S12DP256 — Revision 1.1
Resource Mapping
If conflicts occur when mapping resources, the register block will take
precedence over the other resources; RAM 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. The
following table shows resource mapping precedence. Only one module
will be selected at a time. In the case of more than one module sharing
a space only the highest priority module will be selected. For example, if
the RAM and registers are mapped to the same space, then the first 1K
bytes will be the registers and the section of RAM which “shares” that
space will not be available in the memory map.The remaining RAM will
be visible and available. If the internal RAM, registers or BDM (if active)
are mapped to the same space as the EEPROM, they will have priority
over the EEPROM and the EEPROM locations covered by the RAM,
registers or BDM ROM will not be visible in the memory map.
NOTE: Generally it is not a good idea to map RAM and registers to the same
location because of the significant amount of RAM which would become
unusable
.
In expanded modes, all address space not used by internal resources is
by default external memory.
Table 16 Mapping Precedence
Precedence Resource
Highest
BDM space (Internal) when BDM is active
this 256 byte block of registers and ROM
appear at $FF00 – $FFFF
...
Register Space (Internal) – 1K bytes fully
blocked for registers
... RAM (Internal) – 12K bytes
... EEPROM – 4K bytes
... On-Chip Flash EEPROM – 256K bytes
Lowest Remaining external
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