mc68hc05x4dw Freescale Semiconductor, Inc, mc68hc05x4dw Datasheet - Page 34

• Manufacturer Part Number: mc68hc05x4dw
• Description: Xc68hc705x4 Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Indexed, 8-Bit
Offset
Indexed,16-Bit
Offset
Relative
CPU
MC68HC05X4
Indexed, no offset instructions are often used to move a pointer through
a table or to hold the address of a frequently used RAM or 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.
As with direct and extended addressing, the Motorola assembler
determines the shortest form of indexed addressing.
Relative addressing is only for branch instructions. If the branch
condition is true, the CPU finds the effective branch destination by
adding the signed byte following the opcode to the contents of the
program counter. If the branch condition is not true, the CPU goes to the
next instruction. The offset is a signed, two’s complement byte that gives
a branching range of –128 to +127 bytes from the address of the next
location after the branch instruction.
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CPU
8-cpu