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MC9S08DZ128 Datasheet, PDF (148/458 Pages) Freescale Semiconductor, Inc – Microcontrollers | |||
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Chapter 7 Central Processor Unit (S08CPUV5)
the high-order byte is located in the next memory location after the opcode, and the low-order byte is
located in the next memory location after that.
7.3.4 Direct Addressing Mode (DIR)
In direct addressing mode, the instruction includes the low-order eight bits of an address in the direct page
(0x0000â0x00FF). During execution a 16-bit address is formed by concatenating an implied 0x00 for the
high-order half of the address and the direct address from the instruction to get the 16-bit address where
the desired operand is located. This is faster and more memory efï¬cient than specifying a complete 16-bit
address for the operand.
7.3.5 Extended Addressing Mode (EXT)
In extended addressing mode, the full 16-bit address of the operand is located in the next two bytes of
program memory after the opcode (high byte ï¬rst).
7.3.6 Indexed Addressing Mode
Indexed addressing mode has seven variations including ï¬ve that use the 16-bit H:X index register pair and
two that use the stack pointer as the base reference.
7.3.6.1 Indexed, No Offset (IX)
This variation of indexed addressing uses the 16-bit value in the H:X index register pair as the address of
the operand needed to complete the instruction.
7.3.6.2 Indexed, No Offset with Post Increment (IX+)
This variation of indexed addressing uses the 16-bit value in the H:X index register pair as the address of
the operand needed to complete the instruction. The index register pair is then incremented
(H:X = H:X + 0x0001) after the operand has been fetched. This addressing mode is only used for MOV
and CBEQ instructions.
7.3.6.3 Indexed, 8-Bit Offset (IX1)
This variation of indexed addressing uses the 16-bit value in the H:X index register pair plus an unsigned
8-bit offset included in the instruction as the address of the operand needed to complete the instruction.
7.3.6.4 Indexed, 8-Bit Offset with Post Increment (IX1+)
This variation of indexed addressing uses the 16-bit value in the H:X index register pair plus an unsigned
8-bit offset included in the instruction as the address of the operand needed to complete the instruction.
The index register pair is then incremented (H:X = H:X + 0x0001) after the operand has been fetched. This
addressing mode is used only for the CBEQ instruction.
MC9S08DZ128 Series Data Sheet, Rev. 1
148
Freescale Semiconductor
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