W65C02S Datasheet, PDF (18/40 Pages) List of Unclassifed Manufacturers – Microprocessor

The Western Design Center, Inc.
4.9 Program Counter Relative r
W65C02S Data Sheet
The Program Counter relative addressing mode, sometimes referred to as Relative Addressing, is used with the Branch
instructions. If the condition being tested is met, the second byte of the instruction is added to the Program Counter and
program control is transferred to this new memory location.
Byte:
Instruction:
2
1
0
offset OpCode
New PC value
PCH
PCL
+
offset
effective address
4.10 Stack s
The Stack may use memory from 0100 to 01FF and the effective address of the Stack address mode will always be within
this range. Stack addressing refers to all instructions that push or pull data from the stack, such as Push, Pull, Jump to
Subroutine, Return from Subroutine, Interrupts and Return from Interrupt.
Byte:
Instruction:
2
1
0
OpCode
Operand address:
1
S
4.11 Zero Page zp
With Zero Page (zp) addressing the second byte of the instruction is the address of the operand in page zero.
Byte:
Instruction:
2
1
0
zp
OpCode
Operand address:
0
zp
4.12 Zero Page Indexed Indirect (zp,x)
The Zero Page Indexed Indirect addressing mode is often referred to as Indirect,X. The second byte of the instruction is the
zero page address to which the X Index Register is added and the result points to the low byte of the indirect address.
Byte:
Instru ction:
2
1
0
zp
OpCode
Base Address:
Indirect Address:
+
0
zp
X
address
Operand address:
indirect address
The Western Design Center, Inc.
W65C02S Data Sheet
18