1ECE 274 - Digital LogicLecture 8 Lecture 8 Parallel Load Register Shift Registers Multifunction Registers Multifunction Register Design Process2Digital DesignDatapath Components: Processor: Controller + DatapathData InputsData OutputsControl OutputsControl InputsController Datapath3Digital DesignDatapath Components: Registers Additional Desired Functionality: Ability to choose between previous and new value Load all bits at the same time4Digital DesignDatapath Components: Parallel Load Register 4-bit Parallel Load Register Ability to choose between previous and new value Load all bits at the same time5Digital DesignDatapath Components: Parallel Load Register ExampleBasic parallel load register example.6Digital DesignDatapath Components: Parallel Load Register ExampleBasic register example: (a) timing diagram, and (b) the contents of each register.7Digital DesignDatapath Components: Design Example: Weight Sampler Weight Sampler: Functional Description: Display Weight of objects placed on scale Display “Present weight” Display “Saved weight” stored upon Save button being pressed8Digital DesignDatapath Components: Design Example: Weight SamplerWeight sampler implemented using a 4-bit parallel load register.9Digital DesignSequential Logic Design – Controllers: Design ExampleCircuit Description: Temperature History StorageFunctional Description:Design a system that records the outside temperature every hoursand displays the last three recorded temperatures. Inputs:c: clock signalx4..0: 5-bit temperature readingOutputs:a4..0, b4..0, c4..0: 5-bit temperature readings to be displayed10Digital DesignDatapath ComponentsInternal design of the TemperatureHistoryStorage component, using parallel load registers.11Digital DesignDatapath Components: Design Example: Above Mirror Display12Digital DesignDatapath Components: Design Example: Above Mirror DisplayTAIMxyDI0I1I2I3Ds1s0From the car’sTo the above-mirror displaycentral computer4x18-bitbuttonWe’ll designthis later88888?13Digital DesignDatapath Components: Design Example: Above Mirror DisplayUser Input14Digital DesignDatapath Components: Electronic CheckerboardCircuitCircuit15Digital DesignDatapath Components: Electronic CheckerboardAn electronic checkerboard: Eight 8-bit registers (R7 through R0) can be used to drive the 64 LEDs, using one register per column, and detail of how one register connects to a column’s LEDs.16Digital DesignDatapath Components: Electronic CheckerboardTiming diagram indicating an input sequence that can be used to initialize 17Digital DesignDatapath Components: Electronic CheckerboardCheckerboard after loading registers for initial checker positions.18Digital DesignDatapath Components: Computer Components: Shift RegistersShift Register: Register that can move contents left/right Right shift example: (a) sample contents before and after a right shift, and (b) bit-by-bit view of the shift.19Digital DesignDatapath Components: Computer Components: Shift RegistersShift register: (a) implementation, (b) paths when shr=1, and (c) block symbol. 20Digital DesignDatapath Components: Computer Components: Rotator21Digital DesignDatapath Components: Not really a quiz, but it is a CHALLENGE!!Design a 4-bit shift register with a shift-in input that will allow you to shift left by 0-3 positions on one clock cycle.Clearly indicate the following:InputsOutputsImplementation22Digital DesignDatapath Components: Design Example: Above Mirror DisplayIf you implement this diagram using shift registers, by how many input wires will we need? A) 1 B) 6 C) 823Digital DesignDatapath Components: Design Example: Above Mirror Display24Digital DesignDatapath Components: Computer Components: Multifunction RegistersOperation Table 4-bit register with multiple operations: parallel load shift right25Digital DesignDatapath Components: Computer Components: Multifunction Registers 4-bit register with multiple operations: Parallel load Shift right Shift leftOperation table of a 4-bit register with parallel load, shift left, and shift right operations.26Digital DesignDatapath Components: Computer Components: Multifunction RegistersOperation table of a 4-bit register with separate control inputs for parallel load, shift left, and shift right.27Digital DesignDatapath Components: Computer Components: Multifunction RegistersA small combinational circuit maps the control inputs ld, shr, and shl to the muxselect inputs s1 and s0.28Digital DesignDatapath Components: Computer Components: Multifunction RegistersTruth tables describing operations of a register with left/right shift and parallel load along with the mapping of the register control inputs to the internal 4x1 mux select lines: (a) complete operation table defining the mapping of ld, shr, and shl to s1 and s0, and (b) a compact version of the operation table.29Digital DesignDatapath Components: Computer Components: Multifunction RegistersFour-step process for designing a multifunction register.Create a truth table that maps external control lines to the internal mux select lines, with appropriate priorities, and then design the logic to achieve that mappingMap control lines4.For each operation, connect the corresponding mux data input to the appropriate external input or flip-flop output (possibly passing through some logic) to achieve the desired operation.Connect muxinputs3.Create an operation table defining the desired operation for each possible value of the mux select lines.Create muxoperation table2.Count the number of operations (don’t forget the maintain present value operation!) and add in front of each flip-flop a mux with at least that number of inputs.Determine muxsize1.DescriptionStep30Digital DesignDatapath Components: Using Multifunction Register Design Process Functional Requirements: Register with the following operations Load Shift left Synchronous clear Synchronous set31Digital DesignDatapath Components: Using Multifunction Design Process Step 1: Determine Mux Size Register with the following operations Load Shift left Synchronous clear Synchronous set Don’t forget Hold Present ValueNeed a mux with at least 5 inputs: 8x1 mux32Digital DesignDatapath Components: Using Multifunction Design Process Step 2: Create Mux Operation Table Assign operations to mux inputs33Digital DesignDatapath Components: Using Multifunction Design Process Step 3: