Overview Part 1 - Registers, Microoperations and Implementations Registers and load enable Register transfer operations Microoperations - arithmetic, logic, and shift Microoperations on a single register Multiplexer-based transfers Shift registers Part 2 - Counters, Register Cells, Buses, & Serial Operations Part 3 – Control of Register Transfers

Registers Register a collection of binary storage elements included a set of flip-flop n-bit register store n-bit binary information Frequently used to perform simple data storage and data movement and processing operations

7-1 Register and Load Enable Register with load enable by clock gating States: 22 = 4 Input Combinations: 22 = 4 Output Combinations: 22 = 4 Y = A A(t+1) = IN Moore States = 2n Input Combinations = 2n Output Combinations = 2n

7-1 Register and Load Enable Register with load enable directly through input

7-2 Register transfer Datapath: performs data-processing operations Large digital systems are hard to be designed by using state table in Chap. 5 Large digital systems are often designed by modular, hierarchical approach Large digital systems are partitioned into two types of modules Datapath: performs data-processing operations Control unit: determine the sequence of those operations

7-2 Register transfer The registers are assumed to be basic components of the digital system Register transfer operation: movement on the data stored in register and the processing performed on the data Three basic components The set of registers in digital systems The operations performed on the data Control on the sequence of operations

7-3 Register Transfer Operations Notation for register: uppercase letters (sometime followed by numbers) AR: address register PC: program counter IP: instruction register R2: the register 2

7-3 Register Transfer Operations Data transfer from a register to another one R2 ←R1 Data transfer with conditions If (K1=1) then (R2 ←R1) K1: R2 ←R1 Hardware implementation

7-3 Register Transfer Operations More register transfer operation executed at the same time: K3: R2 ←R1, R1 ←R2

7-4 A note for VHDL and Verilog

7-5 Microoperation An elementary operations performed on data stored in registers or in memory. Transfer Arithmetic Logic: perform bit manipulation on data in register Bitwise AND, Bitwise OR …. Shift

Arithmetic Microoperations

Arithmetic Microoperations The control variable X selects the operation, and the control variable K1 loads the result in to R1. Fig. 7.6 Implementation