1. LC-2: The Little Computer 2
Gabriella Trucco

2. Informazioni
Reference guide available online (google: LC-2 little computer)
Introduction to Computing Systems
From Bits and Gates to C and Beyond
(A First Course in Computer Science and Engineering)

3. Von Neumann model

4. LC-2: example of Von Neumann model

5. Instruction
2 parts
Opcode
Operands
LC-2 instruction: 16 bit

6. Instruction cycle

7. LC-2 overview Memory organization
Address space: 2 16 locations
Addressability: 16 bit
Registers: additional temporary storage locations accessed in a single machine cycle
Registers uniquely identifiable
8 registers, identified by 3 bit register number (R0..R7)
Addressing modes: to specify where the operand is located
Immediate (or literal): operand is part of the instruction
Register
Memory addressing modes
Direct
Indirect
Base + off-set

8. LC-2 overview
Condition codes: allow instruction sequencing to change on the bases of previously generated results
N: negative
Z: zero
P: positive

9. LC-2 instructions

10. Operate instructions
NOT
ADD
AND

11. Data movement Load: from memory to register
Store: from register to memory
LEA: immediate mode
LD and ST: direct mode

12. Data movement
LDI and STI: Indirect mode
LDR and STR: Base + offset

13. Example