[CA] Lecture #08

Unsigned Numbers

 

2s-Complement Signed Integers

 

Signed Negation

1. 숫자 뒤집기
2. +1
3. 부호 붙이기

 

Sign Extension

• + --> 0
• - --> 1

 

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Representing Instructions

: Assembly language --> Binary number

• RISC-V instructions: Encoded as 32-bit instruction words.

 

Hexadecimal

Hexadecimal

 

RISC-V R-format Instructions

R-format

• add  destination, source 1, source 2
• sub  destination, source 1, source 2

▶ function 7, function 3, opcode: Instruction 결정

▶ rd, rs1, rs2: $x0~$x31(32가지) --> 5-bit

 

R-format Example

R-format Example

 

RISC-V I-format Instructions

I-format

• addi  destination, immediate(source)
• lw     destination, immediate(source)

▶ rs1: source or base address

▶ immediate: constant operand or offset

• 2s-complement, sign extended (다른 부분은 모두 unsigned)
• 12 bits --> -2^11~(2^11-1)까지 표현 가능 (2048 bytes, 512 words)

 

I-format Example

I-format Example

 

RISC-V S-format Instructions

S-format

• SW  source 2, immediate(source 1)

▶ rs1: base address

▶ rs2: source operand

▶ immediate: offset

• Split so that rs1 and rs2 fields always in the same place.

 

S-format Example

S-format Example

 

Summary: R, I and S Type Instructions

R, I and S Type Instructions

 

Machine Language

• Machine language: Binary representation used for communication within a computer system.
• Machine code: A sequence of such instructions.
• Instruction format: Layout of the instruction.

 

Example: Translation

A[30] = h + A[30] + 1

Translation into machine languages

 

Stored Program Computers

• Instructions represented in binary, just like data.
• Instructions and data stored in memory.
• Programs can operate on programs.
• Binary compatibility(호환성) allows compiled programs to work on different computers.

 

Example: Check Yourself

Example: Check Yourself