W65C02S Datasheet, PDF (16/40 Pages) List of Unclassifed Manufacturers – Microprocessor

The Western Design Center, Inc.
4 ADDRESSING MODES
W65C02S Data Sheet
The W65C02S is capable of directly addressing 65,536 bytes of memory. The Program Address and Data Address space is
contiguous throughout the 65,536 byte address space. Words, arrays, records, or any data structures may span the 65,536
byte address space. The following addressing mode descriptions provide additional detail as to how effective addresses are
calculated. Sixteen addressing modes are available for the W65C02S. This address space has special significance within
certain addressing modes.
4.1 Absolute a
With Absolute addressing the second and third bytes of the instruction form the 16-bit address.
Byte:
Instruction:
2
ADH
1
ADL
0
OpCode
Operand Address:
ADH
ADL
4.2 Absolute Indexed Indirect (a,x)
With the Absolute Indexed Indirect addressing mode, the X Index Register is added to the second and third byes of the
instruction to form an address to a pointer. This address mode is only used with the JMP instruction and the program
Counter is loaded with the first and second bytes at this pointer.
Byte:
Instruction:
2
ADH
1
ADL
0
OpCode
Indirect Base address:
Indirect address:
New PC value:
ADH
ADL
+
X
effective address
indirect address
4.3 Absolute Indexed with X a,x
With the Absolute Indexed with X addressing mode, the X Index Register is added to the second and third bytes of the
instruction to form the 16-bits of the effective address.
Byte:
Instruction:
2
ADH
1
ADL
0
OpCode
Operand address:
ADH
ADL
+
X
effective address
The Western Design Center, Inc.
W65C02S Data Sheet
16