M68SDIL datasheet(79/432 Pages) MOTOROLA

79 / 432 page

Operating Modes and Resource Mapping

Internal Resource Mapping

68HC(9)12D60 — Rev 4.0

Advance Information

MOTOROLA

Operating Modes and Resource Mapping

EME — Emulate Port E

In single-chip mode PORTE and DDRE are always in the map

regardless of the state of this bit.

0 = PORTE and DDRE are in the memory map.

1 = If in an expanded mode, PORTE and DDRE are removed from the

internal memory map. Removing the registers from the map allows

the user to emulate the function of these registers externally.

Normal modes: write once; special modes: write anytime EXCEPT

the first time. Read anytime.

5.5 Internal Resource Mapping

The internal register block, RAM, and EEPROM have default locations

within the 64K byte 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, in order 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 NOP instruction.

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.

In expanded modes, all address space not used by internal resources is

by default external memory.

The 68HC912D60 contains 60K bytes of Flash EEPROM nonvolatile

memory which can be used to store program code or static data. It is

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

M68SDIL Datasheet(PDF) 79 Page - Motorola, Inc