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CHAPTER 3 REGISTERS
3.5 Index Register (IX) and Extra Pointer (EP)
The index register (IX) and extra pointer (EP) are 16-bit application-specific registers
existing in the CPU.
The index register (IX) adds an 8-bit offset value with its sign to generate the address
stored by the operand.
The extra pointer (EP) indicates the address stored by the operand.
■ Index Register (IX)
Figure 3.5-1 indicates the operation of the index register.
Figure 3.5-1 Operation of Index Register (IX)
■ Extra Pointer (EP)
Figure 3.5-2 shows the operation of the extra pointer.
Figure 3.5-2 Operation of the Extra Pointer (EP)
34H 34H
IX IX
12H 12H
A
A
XXXX
H
5678H
56CFH
56CEH
56CDH
56CCH
1234H
5678H
MOVW A, @IX+55H 5678H+0055H
= 56CDH
+
Before execution MEMORY
After execution
MEMORY
56CFH
56CEH
56CDH
56CCH
34H 34H
12H 12H
EP
EP
Before execution
MEMORY
After execution
1234H
5678H
XXXXH
5678H
5679H
5678H
5677H
5676H
MEMORY
A
A
5679
H
5678H
5677H
5676H
MOVW A, @EP