w65c816s Microprocessor Data Sheet.pdf

The Western Design Center, Inc.W65C816S Data SheetProgram Counter Relative -rThe Program Counter Relative (r) addressing is referred to as Relative Addressing and is used only with theBranch instructions. If the condition being tested is met, the second byte of the instruction is added to the ProgramCounter, which has been updated to point to the OpCode of the next instruction. The offset is a signed 8-bitquantity in the range from -128 to 127. The Program Bank Register is not affected.Stack-sStack (s) addressing refers to all instructions that push or pull data from the stack, such as Push, Pull, Jump toSubroutine, 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,sWith Stack Relative (d,s) addressing the low-order 16 bits of the effective address is formed from the sum of thesecond 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: OpCode offsetStack Pointerthen: + offsetOperand Address: 00 effective addressStack Relative Indirect Indexed-(d,s),yWith Stack Relative Indirect Indexed ((d,s),y) addressing the second byte of the instruction is added to the StackPointer to form a pointer to the low-order 16-bit base address in Bank 0. The Data Bank Register contains thehigh-order 8 bits of the base address. The effective address is the sum of the 24-bit base address and the Y IndexRegister.Instruction: OpCode offsetStack Pointeroffset00 S + offsetthen + DBRbase address+ Y RegOperand Address:effective addressThe Western Design Center W65C816S 26