1. Processor Instructions set. Learning Objectives
Learn how to use mnemonics to write code using assembly language.
Learn the difference between immediate and direct addressing
Learn how to use different types of operation codes: Data transfer, arithmetic operation, logical bitwise operations and branch operations.

2. Processor Instruction Set
Different types of instruction set with different mnemonics
CISC (Complex instruction set)
RISC (Reduced instruction set)
cmp r1, #10
Compare the value in register 1 with the value 10
cmp
R1,
#10
OPCODE
OPERAND
# = Addressing Mode

3. Processor Instruction Set
OPCODE
Mnemonic – style and type determined by the instruction set
Example: CMP, ADD, MOV, LDA
Bits are allocated for opcode, operand and addressing mode
Example – 32 Bit (12 – opcode / 4 – Addressing mode / 16 – Operand)

4. Processor Instruction Set
Addressing
Direct addressing
This is whereby a memory address is provided where the data can be obtained.
LDR r1, 100 ‘load data stored in address 100 into the register
Immediate Addresssing.
This is whereby an actual value is provided rather than a memory address
MOV r1, #10 ‘move the value 10 into the register

5. Processor Instruction Set
Operation codes
Data transfer operations
Moves data between registers and main memory
MOV, STR,LDR (Move, Store, Load)
Arithmetic operations
Opcodes that do basic arithmetic such as subtract, Add, increment, decrement, negate, compare and shift
ADD, SUB, CMP, LSL, LSR etc..
Logical Operations
Performs the logical operations – AND, OR, NOT, XOR
Each bit of the data is compared during the operation
Used to compare values and calculate them.
AND, ORR, EOR, MVN

6. Processor Instruction Set
Operation codes
Branch Operations
Allows a program to branch to another memory address – thereby a different part of the program after evaluating a condition. Or they can branch unconditionally.
B – Branch always
BNE – Branch if not Equal
BEQ – Branch if equal
BGT – Branch if greater than
BLT – Branch if less than
A label then follows the opcode
BGT Alabel

7. Processor Instruction Set
Task
Use the LMC to write a division program that takes in two numbers and outputs both the answer and the remainder.