Map Of Single Cycle Functional Unit

The Datapath with the control unit of a single cycle implementation of MIPS for a subset of instructions add, sub, addi, and, or, slt, beq, j is shown in the following circuit Fig. 1. MIPS single cycle design. For implementing a subset, we need only few bits rather than 6 bits of the opcode and 6 bits of funct field of R-type instructions.

Control Unit Design for Single-Cycle CPU Control Unit Maps instruction to control signals Traditional Control Unit - FSM Produces control signals asserted at different times - Design NSL, SM, OFL Single-Cycle Control Unit - Every cycle we perform the same steps Fetch, Decode, Execute - Signals are not necessarily time

Single-Cycle Datapath and Control Specification Read Section 5.3 of A Simple Implementation in the text book. Verilog code of each functional unit, including data memeory unit, instruction memory unit, sign-extension unit, shift left 2 unit, 32-bit wide 2-to-1 multiplexor, 5-bit wide 2-to-1 multiplexor, program counter, the main control

CSE 141, S2'06 Jeff Brown ALU control bits Recall 5-function ALU based on opcode bits 31-26 and function code bits 5-0 from instruction ALU doesn't need to know all opcodes--we will summarize opcode with ALUOp 2 bits 00 - lw,sw 01 - beq 10 - R-format Main Control op 6 ALU

SINGLE-CYCLE CONTROL Now we have a complete datapathfor our simple MIPS subset -we will show the whole diagram in just a couple of minutes. Before that, we will add the control. The control unit is responsible for taking the instruction and generating the appropriate signals for the datapathelements. Signals that need to be generated include

Today we'll build a single-cycle implementation of this instruction set. All instructions will execute in the same amount of time this will determine the clock cycle time for our performance equations. We'll explain the datapath first, and then make the control unit. Arithmetic add sub and or slt Data Transfer lw sw Control beq

Control unit design Single cycle processor Control unit circuit implementation 2. Computer Organization 1. Analyze instruction set 2. Select datapath components and Could implement entire instruction set as a giant Karnaugh map 17 Control Instruction R-Type ldur b.cond RegWrite 1 1 0 ALUSrc 00 10 XX ALUOp based upon opcode

Single-Cycle Disadvantages amp Advantages n Uses the clock cycle inefficiently -the clock cycle must be timed to accommodate the slowest instruction. n This would be especially problematic for more complex instructions like floating point multiply. n May be wasteful of area. Some functional units e.g., adders, memory must be duplicated since

quotthingsquot using multiple quotfunctional unitsquot In multiprocessing, each thing is processed entirely by a single functional unit e.g. multiple lanes at the supermarket In pipelining, each thing is broken into a sequence of pieces, where each piece is handled by a different specialized functional unit e.g. checker vs. bagger

In the single-cycle implementation, the instruction executes in one cycle by design and the outputs of all functional units must stabilize within one cycle. In contrast, the multicycle implementation uses one or more registers to temporarily store buffer the ALU or functional unit outputs.