1 Pertemuan 20 Microprogrammed Control Matakuliah: H0344/Organisasi dan Arsitektur Komputer Tahun: 2005 Versi: 1/1

2 Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : Menjelaskan konsep dasar microprogrammed control

3 Outline Materi Basic Concepts Microinstruction Sequencing Microinstruction Execution Application of Microprogramming

4 Basic concepts Microinstructions Typical microinstruction formats

5 Basic concepts Organization of control memory

6 Basic concepts Control unit microinstruction

7 Basic concepts Functioning of microprogrammed control unit

8 Basic concepts Wilkes’s microprogrammed control unit

9 Basic concepts Advantages and disadvantage The principal advantage of the use of microprogramming to implement a control unit is that it simplifies the design of control unit. Thus it is both cheaper and less error-prone to implement. A hardwired control unit must contain complex logic for sequencing through the many micro-operations of instruction cycle. On the other hand, the decoder and sequencing logic unit of a microprogrammed control unit are very simple pieces of logic.

10 Microinstruction sequencing The two basic tasks performed by microprogrammed control unit as follows: 1.Microinstruction sequencing 2.Microinstruction execution

11 Microinstruction sequencing Two concerns are involved in he design of microinstruction sequencing technique: the size of microinstruction and address- generation time. The first concern is obvious: minimizing the size of the control memory reduces the cost of that component. The second concern is simply a desire to execute microinstruction as fast possible. Design considerations In executing, a microprogram, the address of the next microinstruction to be executed is in one of these categories: 1.Determined by instruction register 2.Next sequential address 3.Branch

12 Microinstruction sequencing Sequencing techniques 1.Two address fields 2.Single address field 3.Variable format

13 Microinstruction sequencing Branch control logic, two address fields

14 Microinstruction sequencing Branch control logic, single address field

15 Microinstruction sequencing Branch control logic, Variable format

16 Microinstruction sequencing Address generation ExplicitImplicit Two fieldMapping Unconditional branchAddition Conditional branchResidual control

17 Microinstruction executing Control unit organization

18 Microinstruction executing The microinstruction spectrum Characteristics UnencodedHighly encoded Many bitsFew bits Detailed view hardwareAggregated view of hardware Difficult to programEasy to program Concurrency fully exploitedConcurrency not fully exploited Little or no control logicComplex control logic Fast executionSlow execution Optimize performanceOptimize programming Terminology UnpackedPacked HorizontalVertical HardSoft

19 Microinstruction executing Microinstruction encoding

20 Microinstruction executing Vertical microinstruction repertoire

21 Microinstruction executing Horizontal microinstruction repertoire

22 Applications of microprogramming The set of current applications for microprogramming includes Realization of computers Emulation Operating system support Realization of special-purpose devices High level language support Micro diagnostics User tailoring