MC68HC11KW1 Datasheet, PDF (45/238 Pages) Motorola, Inc – High-density complementary metal oxide semiconductor HCMOS) microcontroller unit

4
OPERATING MODES AND ON-CHIP MEMORY ₄
This section contains information about the modes that define MC68HC11KW1 operating 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 (See Table 4-4). Single chip and expanded modes are the normal modes. In single chip
mode only on-board memory is available. Expanded mode, however, allows access to external
memory. Each of these 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 expanded mode that allows privileged access to internal
resources.
4.1.1 Single chip operating mode
In single chip operating mode, the MC68HC11KW1 microcontroller has no external address or
data bus. Ports B, C and F are available for general-purpose parallel I/O.
4.1.2 Expanded operating mode
In expanded operating mode, the MCU can access a 64K byte physical address space. The
address space includes the same on-chip memory addresses used for single chip mode, in
addition to external memory and peripheral devices.The expansion bus is made up of ports B, C,
and F. 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 signals the direction of data
transfer on the port C bus.
The MC68HC11KW1 includes an additional memory expansion feature, available in expanded
modes, which allows access to pages of memory in one or two windows within the 64K byte
physical memory space. This can extend the memory space to more than 1M byte. See
Section 4.4.
MC68HC11KW1
OPERATING MODES AND ON-CHIP MEMORY
4-1