mc68hc912dg128 Freescale Semiconductor, Inc, mc68hc912dg128 Datasheet - Page 35

• Manufacturer Part Number: mc68hc912dg128
• Description: M68hc12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

2.7 Opcodes and Operands
MC68HC912DG128 — Rev 3.0
MOTOROLA
The CPU12 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 that can be represented by 8-bit binary
numbers. To expand the number of opcodes, a second page is added to
the opcode map. Opcodes on the second page are preceded by an
additional byte with the value $18.
To provide additional addressing flexibility, opcodes can also be
followed by a postbyte or extension bytes. Postbytes implement certain
forms of indexed addressing, transfers, exchanges, and loop primitives.
Extension bytes contain additional program information such as
addresses, offsets, and immediate data.
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Central Processing Unit
Opcodes and Operands
Central Processing Unit
Technical Data
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