Freescale Semiconductor, Inc.
Operating Modes
Table 5-1. Mode Selection
BKGD MODB MODA
Mode
Port A
G.P. I/O
Port B
G.P. I/O
ADDR
1
0
0
0
1
Normal Single Chip
Normal Expanded Narrow
1
1
ADDR/DATA
Reserved (Forced to
Peripheral)
1
0
—
—
1
0
0
0
0
1
0
0
1
1
1
0
1
0
1
Normal Expanded Wide
Special Single Chip
ADDR/DATA
G.P. I/O
ADDR/DATA
G.P. I/O
Special Expanded Narrow
Special Peripheral
ADDR/DATA
ADDR/DATA
ADDR/DATA
ADDR
ADDR/DATA
ADDR/DATA
Special Expanded Wide
There are two basic types of operating modes:
Normal modes — some registers and bits are protected
against accidental changes.
Special modes — allow greater access to protected control
registers and bits for special purposes such as testing and
emulation.
For operation above 105°C, the MC68HC912DG128 (M temperature
range product only) is limited to single chip modes of operation.
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.
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 background command, then
activated.
Technical Data
MC68HC912DG128 — Rev 3.0
Operating Modes
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