MC68HC05K1 FREESCALE [Freescale Semiconductor, Inc], MC68HC05K1 Datasheet - Page 96

• Manufacturer Part Number: MC68HC05K1
• Description: HCMOS Microcontroller Unit
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Technical Data
10.3.5 Indexed, No Offset
10.3.6 Indexed, 8-Bit Offset
10.3.7 Indexed, 16-Bit Offset
Technical Data
Indexed instructions with no offset are 1-byte instructions that can
access data with variable addresses within the first 256 memory
locations. The index register contains the low byte of the effective
address of the operand. The CPU automatically uses $00 as the high
byte, so these instructions can address locations $0000–$00FF.
Indexed, no offset instructions are often used to move a pointer through
a table or to hold the address of a frequently used random-access
memory (RAM) or input/output (I/O) location.
Indexed, 8-bit offset instructions are 2-byte instructions that can access
data with variable addresses within the first 511 memory locations. The
CPU adds the unsigned byte in the index register to the unsigned byte
following the opcode. The sum is the effective address of the operand.
These instructions can access locations $0000–$01FE.
Indexed 8-bit offset instructions are useful for selecting the kth element
in an n-element table. The table can begin anywhere within the first 256
memory locations and could extend as far as location 510 ($01FE). The
k value is typically in the index register, and the address of the beginning
of the table is in the byte following the opcode.
Indexed, 16-bit offset instructions are 3-byte instructions that can access
data with variable addresses at any location in memory. The CPU adds
the unsigned byte in the index register to the two unsigned bytes
following the opcode. The sum is the effective address of the operand.
The first byte after the opcode is the high byte of the 16-bit offset; the
second byte is the low byte of the offset.
Indexed, 16-bit offset instructions are useful for selecting the kth element
in an n-element table anywhere in memory.
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Instruction Set
MC68HC05K0 • MC68HC05K1 — Rev. 2.0