MC68HC711PH8 Motorola, MC68HC711PH8 Datasheet - Page 47

• Manufacturer Part Number: MC68HC711PH8
• Description: High-density Complementary Metal Oxide Semiconductor (HCMOS) Microcomputer Unit
• Manufacturer: Motorola

PH8.DS03/Modes+mem
OPERATING MODES AND ON-CHIP MEMORY
This section contains information about the modes that define MC68HC11PH8 operating conditions,
and about the on-chip memory that allows the MCU to be configured for various applications.
3.1
The values of the mode select inputs MODB and MODA during reset determine the operating
mode (See Table 3-4). 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 mode that allows privileged access to internal resources.
3.1.1
In single chip operating mode, the MC68HC11PH8 microcontroller has no external address or
data bus. Ports B, C, F, and the R/W pin are available for general purpose parallel I/O.
3.1.2
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, 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/PG7 pin signals the direction of data transfer on the port C bus.
When internal resources are accessed in expanded mode, the last external address can be held on
the output pins (A[15:0]) in order to reduce radio-frequency interference (RFI) emissions. This function
is controlled by the FREEZ bit in the CONFIG register. See Section 3.3.2.1 for a description of this bit.
To allow access to slow peripherals, off chip accesses can be extended by one E clock cycle, under
control of the STRCH and STRX bits (in the OPT2 and INIT2 registers respectively). The E clock
MC68HC11PH8
Operating modes
Single chip operating mode
Expanded operating mode
OPERATING MODES AND ON-CHIP MEMORY
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