mc68hc11d0cfn2 Freescale Semiconductor, Inc, mc68hc11d0cfn2 Datasheet - Page 41

• Manufacturer Part Number: mc68hc11d0cfn2
• Description: M68hc11 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

3.3 Data Types
3.4 Opcodes and Operands
3.5 Addressing Modes
MC68HC711D3 — Rev. 2
MOTOROLA
and processing continues to the next instruction. S is set by reset; STOP is
disabled by default.
The M68HC11 CPU supports four data types:
A byte is eight bits wide and can be accessed at any byte location. A word is
composed of two consecutive bytes with the most significant byte at the lower
value address. Because the M68HC11 is an 8-bit CPU, there are no special
requirements for alignment of instructions or operands.
The M68HC11 Family of microcontrollers uses 8-bit opcodes. Each opcode
identifies a particular instruction and associated addressing mode to the CPU.
Several opcodes are required to provide each instruction with a range of
addressing capabilities. Only 256 opcodes would be available if the range of values
were restricted to the number able to be expressed in 8-bit binary numbers.
A 4-page opcode map has been implemented to expand the number of
instructions. An additional byte, called a prebyte, directs the processor from page 0
of the opcode map to one of the other three pages. As its name implies, the
additional byte precedes the opcode.
A complete instruction consists of a prebyte, if any, an opcode, and zero, one, two,
or three operands. The operands contain information the CPU needs for executing
the instruction. Complete instructions can be from one to five bytes long.
Six addressing modes can be used to access memory:
These modes are detailed in the following paragraphs. All modes except inherent
mode use an effective address. The effective address is the memory address from
1. Bit data
2. 8-bit and 16-bit signed and unsigned integers
3. 16-bit unsigned fractions
4. 16-bit addresses
1. Immediate
2. Direct
3. Extended
4. Indexed
5. Inherent
6. Relative
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Central Processor Unit (CPU)
Central Processor Unit (CPU)
Data Types
Data Sheet
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