M68HC11E Family — Rev. 5
Data Sheet
MOTOROLA
Operating Modes and On-Chip Memory
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Data Sheet — M68HC11E Family
Section 2. Operating Modes and On-Chip Memory
2.1 Introduction
This section contains information about the operating modes and the on-chip
memory for M68HC11 E-series MCUs. Except for a few minor differences,
operation is identical for all devices in the E series. Differences are noted where
necessary.
2.2 Operating Modes
The values of the mode select inputs MODB and MODA during reset determine the
operating mode. Single-chip and expanded multiplexed are the normal modes.
In single-chip mode only on-chip memory is available.
Expanded mode, however, allows access to external memory.
Each of the two normal modes is paired with a special mode:
Bootstrap, a variation of the single-chip mode, is a special mode that
executes a bootloader program in an internal bootstrap ROM.
Test is a special mode that allows privileged access to internal resources.
2.2.1 Single-Chip Mode
In single-chip mode, ports B and C and strobe pins A (STRA) and B (STRB) are
available for general-purpose parallel input/output (I/O). In this mode, all software
needed to control the MCU is contained in internal resources. If present, read-only
memory (ROM) and/or erasable, programmable read-only memory (EPROM) will
always be enabled out of reset, ensuring that the reset and interrupt vectors will be
available at locations $FFC0–$FFFF.
NOTE:
For the MC68HC811E2, the vector locations are the same; however, they are
contained in the 2048-byte EEPROM array.
2.2.2 Expanded Mode
In expanded operating mode, the MCU can access the full 64-Kbyte address
space. The space includes:
The same on-chip memory addresses used for single-chip mode
Addresses for external peripherals and memory devices
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