
Operating Modes and Resource Mapping
Mode and Resource Mapping Registers
Data Sheet
MC68HC812A4 — Rev. 6.0
Operating Modes and Resource Mapping
5.5 Mode and Resource Mapping Registers
This section describes the mode and resource mapping registers.
5.5.1 Mode Register
MODE controls the MCU operating mode and various configuration
options. This register is not in the map in peripheral mode.
Read: Anytime
Write: Varies from bit to bit
SMODN, MODB, and MODA — Mode Select Special, B, and A Bits
These bits show the current operating mode and reflect the status of
the BKGD, MODB, and MODA input pins at the rising edge of reset.
SMODN can be written only if SMODN = 0 (in special modes) but the
first write is ignored. MODB and MODA may be written once if
SMODN = 1; anytime if SMODN = 0, except that special peripheral
and reserved modes cannot be selected.
Address: $000B
Bit 7
65
432
1
Bit 0
Read:
SMODN
MODB
MODA
ESTR
IVIS
0
EMD
EME
Write:
Reset States
Special single-chip:
0
1
0
1
Special expanded narrow:
0
1
0
1
Peripheral:
0
1
0
1
0
1
Special expanded wide:
0
1
0
1
Normal single-chip:
100
00
Normal expanded narrow:
1
0
1
0
Normal expanded wide:
1
0
Figure 5-1. Mode Register (MODE)
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Freescale Semiconductor, Inc.
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