1. Stack Relative Deferred (sf) Indexed (x) Stack Indexed (sx)
PEP8 Addressing Modes
Immediate (i)
Direct (d)
Indirect (n)
Stack Relative (s)
Stack Relative Deferred (sf)
Indexed (x)
Stack Indexed (sx)
Stack Indexed Deferred (sxf) 2

2. Operand is part of instruction Operand = Operand Specifier
Immediate Addressing
Operand is part of instruction
Operand = Operand Specifier
e.g. ADDA d#5, i
Add 5 to contents of accumulator
d# stands for Decimal and i stands for immediate
5 is operand 3

3. Operand Specifier contains address of operand
Direct Addressing
Operand Specifier contains address of operand
Operand = Memory [Operand Specifier]
e.g. ADDA h#004A, d
Add content of memory location 004A to accumulator
h# stands for hexadecimal and d stands for direct. 5

4. Direct Addressing Diagram
Instruction
Instruction
Specifier
Operand Specifier
Memory
Operand 6

5. Indirect Addressing
Memory cell pointed to by Operand Specifier contains the address of the operand
Operand = Memory[ Memory [Operand Specifier]]
e.g. ADDA h#004A,n
Add contents of cell pointed to by contents of 004A to accumulator
n stands for indirect 7

6. Indirect Addressing Diagram
Operand Specifier
Instruction
Memory
Operand
Pointer to operand
Specifier 9

7. Stack Relative Addressing
Operand is on the stack
Operand = Memory [Stack Pointer + Operand Specifier]
e.g. ADDA d#-1,s
Add contents of cell SP - 1 to accumulator
s stands for stack relative 17

8. Stack Relative Addressing
Operand Specifier
Instruction
Memory
Operand
Stack Pointer
Specifier +

9. Stack Relative Deferred Addressing
Operand is on the stack
Operand = Memory [Memory [SP + Operand Specifier]]
e.g. ADDA d#-4, sf
Add contents of cell pointed to by contents of SP - 4 to accumulator
sf stands for Stack Relative Deferred 17

10. Stack Relative Deferred Addressing
Stack Pointer
Pointer to operand
Operand Specifier
Instruction
Memory
Operand
Specifier +

11. Indexed Addressing e.g. ADDA h#004A, x
Operand = Memory [Index Register + Operand Specifier]
e.g. ADDA h#004A, x
Add contents of cell pointed to by X + 004A to accumulator
x stands for indexed 19

12. Indexed Addressing Instruction Operand Specifier Memory +
Index Register
Specifier +

13. Stack Indexed Addressing
Operand = Memory [SP + X + Operand Specifier]
e.g. ADDA h#004A, sx
Add contents of cell pointed to by SP + X + 004A to accumulator
sx stands for stack indexed 19

14. Stack Indexed Addressing
Stack Pointer
Operand Specifier
Instruction
Memory
Operand
Specifier +
Index Register

15. Stack Indexed Deferred Addressing
Operand = Memory [X + Memory [ SP + Operand Specifier]]
e.g. ADDA h#004A, sxf
Add contents of cell pointed to by X + contents of SP + 004A to accumulator
sxf stands for Stack Indexed Deferred 19

16. Stack Indexed Deferred Addressing
Stack Pointer
Pointer to operand
Operand Specifier
Instruction
Memory
Operand
Specifier +
Index Register