CPU FUNCTIONS — THE INSTRUCTION CYCLE 1. SLIDE TITLE Main Title: CPU FUNCTIONS — THE INSTRUCTION CYCLE Suggested Design: Use a 4-step circular process diagram that continuously repeats, rather than long paragraphs of text. 2. THE 4 STEPS OF THE INSTRUCTION CYCLE FETCH → DECODE → EXECUTE → STORE (WRITEBACK) Step 1: FETCH — Retrieve the Instruction • Operation: The CPU accesses main memory (RAM) to retrieve the next instruction to be executed. • Details: The instruction address is managed by the Program Counter (PC) and the instruction is loaded into the Instruction Register (IR). Step 2: DECODE — Decode the Instruction • Operation: The Control Unit (CU) analyzes and decodes the retrieved instruction. • Details: The CPU determines what operation needs to be performed—such as addition, subtraction, data movement, or comparison—and identifies where the required operands are located. Step 3: EXECUTE — Execute the Instruction • Operation: The Arithmetic Logic Unit (ALU) receives the instruction and performs the required operation. • Details: The CPU performs arithmetic calculations, logical comparisons, or data transfers according to the instruction. Step 4: STORE (WRITEBACK) — Store the Result • Operation: The completed result is written to the designated storage location. • Details: The result is stored in internal CPU registers or written back to RAM, where it can be accessed by other instructions or applications.
CPU FUNCTIONS — THE INSTRUCTION CYCLE
1. SLIDE TITLE
Main Title: CPU FUNCTIONS — THE INSTRUCTION CYCLE
Suggested Design: Use a 4-step circular process diagram that continuously repeats, rather than long paragraphs of text.
2. THE 4 STEPS OF THE INSTRUCTION CYCLE
FETCH → DECODE → EXECUTE → STORE (WRITEBACK)
Step 1: FETCH — Retrieve the Instruction
• Operation: The CPU accesses main memory (RAM) to retrieve the next instruction to be executed.
• Details: The instruction address is managed by the Program Counter (PC) and the instruction is loaded into the Instruction Register (IR).
Step 2: DECODE — Decode the Instruction
• Operation: The Control Unit (CU) analyzes and decodes the retrieved instruction.
• Details: The CPU determines what operation needs to be performed—such as addition, subtraction, data movement, or comparison—and identifies where the required operands are located.
Step 3: EXECUTE — Execute the Instruction
• Operation: The Arithmetic Logic Unit (ALU) receives the instruction and performs the required operation.
• Details: The CPU performs arithmetic calculations, logical comparisons, or data transfers according to the instruction.
Step 4: STORE (WRITEBACK) — Store the Result
• Operation: The completed result is written to the designated storage location.
• Details: The result is stored in internal CPU registers or written back to RAM, where it can be accessed by other instructions or applications.
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The instruction cycle consists of a four-step process: Fetch, where the Program Counter selects and the Instruction Register receives the instruction; Decode, where the Control Unit identifies the operation and operands. Following this, the Execute phase involves the Arithmetic Logic Unit performing calculations or transfers, and Store, where results are written to registers or RAM. This cycle repeats, with each result enabling the next instruction.