MC68HC11F1_13 Datasheet, PDF (39/158 Pages) Freescale Semiconductor, Inc – Technical Data

Freescale Semiconductor, Inc.
SECTION 4OPERATING MODES AND ON-CHIP MEMORY
This section contains information about the modes that define MC68HC11F1 operat-
ing conditions, and about the on-chip memory that allows the MCU to be configured
for various applications.
4.1 Operating Modes
The values of the mode select inputs MODB and MODA during reset determine the
operating mode. Single chip and expanded modes are the normal modes. In single-
chip mode only on-board resources are available. Expanded mode, however, allows
access to external memory or peripheral devices. Each of these two normal modes is
paired with a special mode. Bootstrap mode, a variation of the single-chip mode, exe-
cutes a bootloader program from an internal bootstrap ROM. Test mode allows privi-
leged access to internal resources.
4.1.1 Single-Chip Operating Mode
In single-chip operating mode, the MC68HC11F1 has no external address or data bus.
Ports B, C, and F are available for general-purpose I/O.
4.1.2 Expanded Operating Mode
In expanded operating mode, the MCU can access a 64-Kbyte physical address
space. The address space includes the same on-chip memory addresses used for sin-
gle-chip mode, in addition to external memory and peripheral devices.
The expansion bus is made up of ports B, C, F and the R/W signal. In expanded mode,
high order address bits are output on the port B pins, low order address bits on the port
F pins, and the data bus on port C. The R/W pin indicates the direction of data transfer
on the port C bus.
4.1.3 Special Test Mode
Special test mode, a variation of the expanded mode, is primarily used during Motor-
ola's internal production testing; however, it is accessible for programming the CON-
FIG register, programming calibration data into EEPROM, and supporting emulation
and debugging during development.
4.1.4 Special Bootstrap Mode
Bootstrap mode is a special variation of the single-chip mode. Bootstrap mode allows
special-purpose programs to be entered into internal RAM. When boot mode is select-
ed at reset, a small bootstrap ROM becomes present in the memory map. Reset and
interrupt vectors are located in bootstrap ROM at $BFC0–$BFFF. The MCU fetches
the reset vector, then executes the bootloader.
OPERATING MODES AND ON-CHIP MEMORY
TECHNICAL DATA
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