Chapter 7 Register & Register Transfer 7-1 Register and Register Enable 7-2 Register Transfers 7-3 Register Transfer Operations 7-5 Microoperations 7-6 Microoperations on a Single Register 7-7 Register Cell Design 7-8 MUX and BUS-Based Transfers for Multiple Registers 7-9 Serial Transfers and Microoperations

7-1 Register and Load Enable Def. of Register and Counter Registers A set of flip-flops n-bit register : Including n F/Fs, storing n bits of binary information Counter : A register that goes through a predetermined sequence of states upon the application of clock pulses. : The gates in the counter are connected to in such a way as to produce the prescribed sequence of binary states. ☞ Registers are useful for storing and manipulating information Counters are employed in circuits that sequence and control operations in a digital system.

Clear should be maintained logic "1" during normal clocked operation. It goes to logic "0" only when a system reset is desired. Fig Bit Register

4-Bit Register (Fig.7-1) Logic diagram Symbol

4-Bit Register (Fig.7-1) Load 제어 입력 Timing diagram  Register with parallel load C inputs = Load ＋ Clock  If Load = 1. C inputs = Clock. Reg. is clocked normally, and new info. can be transferred into the register on ↑ of the clock.  If Load = 0, C inputs = 1. Then there is no ↑ transition on the C inputs, so the contents of the Reg. remain unchanged. ; Clock gating.

4-Bit Register with Parallel Load (Fig.7-2) Load determines whether the next pulse will accept new info. or leave the info. in the register intact.

4-Bit Register with Parallel Load (Fig.7-2)

7-2 Register Transfer ( 레지스터 이동 ) Digital system  Partitioned into modular subsystems. ; subsystem 은 특정한 함수연산 수행.  Module ; Register, Counters, Decoders, Multiplexers, Buses, Arithmetic elements, Flip-Flops, 그리고 초기 gates 등과 같은 함수 블록 (functional block) 들로부터 계층적으로 구성되어 진다.  이러한 여러 종류의 subsystem 을 data 및 control 신호를 통하여 서로 연 결하여 하나의 digital system 이 구성된다.

Digital system 을 구성하는 module Datapath ( 데이터 처리장치 ) ; Performs data-processing operation Control Unit ( 제어장치 ) ; Determines the sequence of those operations.

Datapaths and Control Unit Control signals are binary signals that activates the various data-processing operations. To activate the sequence of operations 1.Control unit sends the proper sequence of control signals to datapath. 2.Control unit receives status bits from datapath. 이 변수는 datapath 의 상태를 나 타낸다. 3.Control unit 는 이러한 변수를 이용하여 수행되어야 할 operation 의 순서를 결정 한다. Datapath 와 Control Unit 간의 상호 작용 (Fig 7-3)

Datapaths and Control unit Datapaths 와 Control Unit 는 data inputs, data outputs, control inputs, control output 으로 표시된 통로를 통하여 메모리와 입출력 논리회로와 정보를 교환한다. Datapath 와 Control Unit 간의 상호 작용 (Fig 7-3)

Datapath 란 ? Datapath 의 Registers 와 그 Register 에 저장된 binary data 에 대하여 실행되는 operation 에 의하여 define 된다 Register operations 의 종류 ; shift, count, clear, and load. Register Transfer operations ( 레지스터 이동연산 ) ; Register 내에 저장된 data 의 이동과 register 내에 저장된 data 에 대하여 수행 되는 process Digital System Register Transfer Operation 1. the set of registers in the system 2. the operations that are performed on the data stored in the registers 3. the control that supervises the sequence of operations in the system

Microoperation ( 마이크로연산 ) Register 내에 저장된 data 에 대하여 수행되는 elementary operation ( 예 ) Loading the contents of one register to another Adding the contents of two register Incrementing the contents of register Register 가 수행할 수 있는 elementary operation ( 기본연산 ) ; Load, Count, Add, Subtract, and Shift