Processor Module Integration using Sequential/Pipelined 

D] Integrated processor 

i. Brief Description of the Processor

This 16-bit processor is designed with a single address format and supports indirect addressing mode. Indirect addressing allows more flexible access to data, where the operand in the instruction points to a memory location that holds the actual address of the data. The processor consists of essential modules such as the Program Counter (PC), Memory Address Register (MAR), Instruction Register (IR), ALU, and control unit, each working together to execute instructions through a structured fetch-decode-execute-write back cycle. This design enables efficient handling of memory-based operations, especially useful for array and pointer manipulation.

ii. Instruction State Diagram

The instruction execution in this processor follows a standard five-state cycle:

1. Instruction Fetch (IF):

   • PC sends the address to MAR.

   • The memory outputs the instruction at that address.

   • The instruction is stored in the IR.

2. Instruction Decode (ID):

   • The control unit decodes the opcode and identifies the addressing mode.

   • If indirect addressing is used, the operand is treated as a pointer to the actual data.

3. Operand Fetch (OF):

   • The operand from the IR is sent to the MAR.

   • The data at the address specified by the operand is fetched from memory and loaded into a temporary register.

4. Execution (EX):

   • The ALU performs the operation specified by the opcode using the fetched operand and any required registers.

5. Write Back (WB):

   • The result is written back to the appropriate register or memory location, depending on the instruction.

iii. Microinstructions for the Instructions (in Detail)

Here are detailed microinstructions for two example instructions:

1. LOAD (Indirect Addressing Mode)

Operation: Load data from memory to a register using an indirect address.

• Step 1: Fetch the instruction.

  • MAR ← PC

  • MBR ← Memory[MAR]

  • IR ← MBR

  • PC ← PC + 1

• Step 2: Decode the instruction.

  • Decode opcode and addressing mode

• Step 3: Fetch the operand.

  • MAR ← IR[Operand]

  • MBR ← Memory[MAR]

  • Temp ← MBR

• Step 4: Execute the LOAD operation.

  • Register ← Temp

2. ADD (Indirect Addressing Mode)

Operation: Add the value from memory (indirect address) to a register.

• Step 1: Fetch the instruction.

  • MAR ← PC

  • MBR ← Memory[MAR]

  • IR ← MBR

  • PC ← PC + 1

• Step 2: Decode the instruction.

  • Decode opcode and addressing mode

• Step 3: Fetch the operand.

  • MAR ← IR[Operand]

  • MBR ← Memory[MAR]

  • Temp ← MBR

• Step 4: Execute the ADD operation.

  • ALU ← Register + Temp

  • Register ← ALU Result

These microinstructions ensure that the processor correctly handles indirect addressing and performs the intended operations efficiently. Each step corresponds to a control signal sequence generated by the control unit, ensuring proper coordination between the modules.

DELIVERABLES:

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