MC68HC912BD32 Datasheet, PDF (48/292 Pages) Freescale Semiconductor, Inc – Advance Information

Freescale Semiconductor, Inc.
Operating Modes and Resource Mapping
Table 10 Mode Selection
BKGD
0
0
0
0
1
1
1
1
MODB MODA
Mode
0
0
Special Single Chip
0
1
Special Expanded Narrow
1
0
Special Peripheral
1
1
Special Expanded Wide
0
0
Normal Single Chip
0
1
Normal Expanded Narrow
1
0 Reserved (Forced to Peripheral)
1
1
Normal Expanded Wide
Port A
General Purpose I/O
ADDR[15:8]/DATA[7:0]
ADDR/DATA
ADDR/DATA
General Purpose I/O
ADDR[15:8]/DATA[7:0]
—
ADDR/DATA
Port B
General Purpose I/O
ADDR[7:0]
ADDR/DATA
ADDR/DATA
General Purpose I/O
ADDR[7:0]
—
ADDR/DATA
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.
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.
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.
Normal Expanded
Wide Mode
This is a normal mode of operation in which the address and data are
multiplexed onto ports A and B. ADDR[15:8] and DATA[15:8] are
present on port A. ADDR[7:0] and DATA[7:0] are present on port B.
Normal Expanded
Narrow Mode
Port A is configured as the high byte of address multiplexed with the 8-bit
data bus. Port B is configured as the lower 8-bit address bus. This mode
is used for lower cost production systems that use 8-bit wide external
EEPROMs or RAMs. Such systems take extra bus cycles to access
MC68HC912BD32 Rev 1.0
Operating Modes and Resource Mapping
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2-mode