Chapter 7 – Registers and Register Transfers Part 1 – Registers, Microoperations and Implementations Logic and Computer Design Fundamentals

2 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

3 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

4 7-1 Register and Load Enable Register with load enable by clock gating

5 7-1 Register and Load Enable Register with load enable directly through input

6 7-2 Register transfer  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 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

8 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

9 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

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

A note for VHDL and Verilog

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

13 Arithmetic Microoperations

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