XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 78

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

Operating Modes and Resource Mapping
5.2.1 Normal Operating Modes
5.2.1.1 Normal Expanded Wide Mode
5.2.1.2 Normal Expanded Narrow Mode
5.2.1.3 Normal Single-Chip Mode
5.2.2 Special Operating Modes
5.2.2.1 Special Expanded Wide Mode
Data Sheet
78
The two basic types of operating modes are:
A system development and debug feature, background debug mode (BDM) is
available in all modes. In special single-chip mode, BDM is active immediately after
reset.
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.
The 16-bit external address and data buses use ports A and B. ADDR15–ADDR8
and DATA15–DATA8 are multiplexed on port A. ADDR7–ADDR0 and
DATA7–DATA0 are multiplexed on port B.
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 A. ADDR15–ADDR8 and
DATA7–DATA0 are multiplexed on port A.
Normal single-chip mode has no external buses. Ports A, B, and E are configured
for general-purpose input/output (I/O). Port E bits 1 and 0 are input only with
internal pullups and the other 22 pins are bidirectional I/O pins that are initially
configured as high-impedance inputs. Port E pullups are enabled on reset. Port A
and B pullups are disabled on reset.
Special operating modes are commonly used in factory testing and system
development.
This mode is for emulation of normal expanded wide mode and emulation of
normal single-chip mode with a 16-bit bus. The bus-control pins of port E are all
configured for their bus-control output functions rather than general-purpose I/O.
1. Normal modes — Some registers and bits are protected against accidental
2. Special modes — Protected control registers and bits are allowed greater
changes.
access for special purposes such as testing and emulation.
Operating Modes and Resource Mapping
M68HC12B Family — Rev. 8.0
MOTOROLA