Freescale Semiconductor, Inc.
Instruction Set
Addressing Modes
12.3.1 Inherent
Inherent instructions are those that have no operand, such as return
from interrupt (RTI) and stop (STOP). Some of the inherent instructions
act on data in the CPU registers, such as set carry flag (SEC) and
increment accumulator (INCA). Inherent instructions require no operand
address and are one byte long.
12.3.2 Immediate
Immediate instructions are those that contain a value to be used in an
operation with the value in the accumulator or index register. Immediate
instructions require no operand address and are two bytes long. The
opcode is the first byte, and the immediate data value is the second byte.
12.3.3 Direct
Direct instructions can access any of the first 256 memory locations with
two bytes. The first byte is the opcode, and the second is the low byte of
the operand address. In direct addressing, the CPU automatically uses
$00 as the high byte of the operand address.
12.3.4 Extended
Extended instructions use three bytes and can access any address in
memory. The first byte is the opcode; the second and third bytes are the
high and low bytes of the operand address.
When using the Motorola assembler, the programmer does not need to
specify whether an instruction is direct or extended. The assembler
automatically selects the shortest form of the instruction.
MC68HC705C8A — Rev. 3
MOTOROLA
Technical Data
Instruction Set
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