MC68HC812A4 Datasheet, PDF (81/342 Pages) Motorola, Inc – 16-bit device composed of standard on-chip peripheral modules connected by an intermodule bus. Modules include

Operating Modes and Resource Mapping
Operating Modes
5.3.1 Normal Operating Modes
These modes provide three operating configurations. Background
debugging is available in all three modes, but must first be enabled for
some operations by means of a BDM command. BDM can then be made
active by another BDM command.
5.3.1.1 Normal Expanded Wide Mode
The 16-bit external address bus uses port A for the high byte and port B
for the low byte. The 16-bit external data bus uses port C for the high
byte and port D for the low byte.
5.3.1.2 Normal Expanded Narrow Mode
The 16-bit external address bus uses port A for the high byte and port B
for the low byte. The 8-bit external data bus uses port C. In this mode,
16-bit data is presented high byte first, followed by the low byte. The
address is automatically incremented on the second cycle.
5.3.1.3 Normal Single-Chip Mode
There are no external buses in normal single-chip mode. The MCU
operates as a stand-alone device and all program and data resources
are on-chip. Port pins can be used for general-purpose I/O
(input/output).
Advance Information
MOTOROLA
Operating Modes and Resource Mapping
MC68HC812A4 — Rev. 3.0
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