W65C816S Datasheet, PDF (26/62 Pages) List of Unclassifed Manufacturers – Microprocessor

The Western Design Center, Inc.
W65C816S Data Sheet
Program Counter Relative -r
The Program Counter Relative (r) addressing is referred to as Relative Addressing and is used only with the
Branch instructions. If the condition being tested is met, the second byte of the instruction is added to the Program
Counter, which has been updated to point to the OpCode of the next instruction. The offset is a signed 8-bit
quantity in the range from -128 to 127. The Program Bank Register is not affected.
Stack -s
Stack (s) 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. The bank address is always 0.
Interrupt Vectors are always fetched from Bank 0.
Stack Relative -d,s
With Stack Relative (d,s) addressing the low-order 16 bits of the effective address is formed from the sum of the
second byte of the instruction and the stack pointer. The high-order 8 bits of the effective address are always zero.
The relative offset is an unsigned 8-bit quantity in the range of 0 to 255.
Instruction:
then:
Operand Address:
OpCode
+
00
offset
Stack Pointer
offset
effective address
Stack Relative Indirect Indexed-(d,s),y
With Stack Relative Indirect Indexed ((d,s),y) addressing the second byte of the instruction is added to the Stack
Pointer to form a pointer to the low-order 16-bit base address in Bank 0. The Data Bank Register contains the
high-order 8 bits of the base address. The effective address is the sum of the 24-bit base address and the Y Index
Register.
Instruction:
then
+
+
Operand Address:
OpCode offset
Stack Pointer
offset
00
S + offset
DBR
base address
Y Reg
effective address
The Western Design Center
W65C816S
26