XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 77

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

5.1 Introduction
5.2 Operating Modes
M68HC12B Family — Rev. 8.0
MOTOROLA
Data Sheet — M68HC12B Family
The MCU can operate in eight different modes. Each mode has a different default
memory map and external bus configuration. After reset, most system resources
can be mapped to other addresses by writing to the appropriate control registers.
The states of the BKGD, MODB, and MODA pins during reset determine the
operating mode after reset.
The SMODN, MODB, and MODA bits in the MODE register show current operating
mode and provide limited mode switching during operation. The states of the
BKGD, MODB, and MODA pins are latched into these bits on the rising edge of the
reset signal. During reset an active pullup is connected to the BKGD pin (as input)
and active pulldowns are connected to the MODB and MODA pins. If an open
occurs on any of these pins, the device will operate in normal single-chip mode.
BKGD
0
0
0
0
1
1
1
1
Section 5. Operating Modes and Resource Mapping
MODB
0
0
1
1
0
0
1
1
Operating Modes and Resource Mapping
MODA
0
1
0
1
0
1
0
1
Table 5-1. Mode Selection
Special expanded narrow
Normal expanded narrow
Special expanded wide
Normal expanded wide
(forced to peripheral)
Special single chip
Normal single chip
Special peripheral
Reserved
Mode
purpose I/O
ADDR[15:8]
purpose I/O
ADDR[15:8]
DATA[7:0]
DATA[7:0]
General-
General-
Port A
ADDR
ADDR
ADDR
DATA
DATA
DATA
—
purpose I/O
purpose I/O
ADDR[7:0]
ADDR[7:0]
General-
General-
Data Sheet
Port B
ADDR
ADDR
ADDR
DATA
DATA
DATA
—
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