Memory
A grid of storage cells (latches or flip-flops) organized into addressable locations.
Address Lines
The input that selects which location to read from or write to.
Data Lines
Carry the actual data being written (D_in) or read (D_out)
Write Enable (WE)
Control line specifies the operation: Read (WE = 0) or Write (WE = 1)
Addressability
The number of bits stored in each location (the memory “width”). Common addressability is 8 bits (a byte).
Address Space
The total number of unique locations. For a memory with N address lines, the address space is 2^N.
Decoder
Its job is to take the binary address and activate a single “word line” corresponding to that address.
Control Unit
Coordinates and directs the operation of the computer by using a FSM and clock. It manages the program counter (PC) and instructor register (IR) to control instruction flow and execution.
Processing Unit
Contains the Arithmetic Logic Unit (ALU) for performing calculations and the register file for storing operands, improving performance by reducing memory accesses.
Memory Unit
Stores data and programs while serving as the interface for all input/output operations between the computer and external devices.
Opcode
A code that identifies the operation
Registers
The id number of each source register, up to two, and destination register.
Immediate
A binary value, usually two’s complement, that is stored directly in the instruction and therefore available immediately.
Fixed Bits
Some instructions can be represented without using all of the bits. The ISA will define these bits to be specific values .
Execution Cycle
Fetch, Decode, Execute, Memory Writeback, Register Writeback
Fetch
The control unit retrieves the next instruction from memory using the address in the program counter (PC) and stores it in the instruction register (IR) for processing.
Decode
The control unit interprets the instruction in the IR and reads any required operands, preparing the system for the correct execution steps based on the instruction type.
Execute
The ALU performs the operation specified by the instruction, producing a result or preparing for memory access.
Memory Writeback
Handles data transfer between the processor and data memory, executing load or store operations as needed to retrieve or save data
Register Writeback
Writes the final result of the operation into the destination register and updates the program counter (PC) to point to the next instruction.
