Chapter 3 Flashcards
What does the Control Unit do?
Manages other components of the CPU
What does the Arithmetic Logic Unit do?
Carries out mathematical calculations
What are registers?
Small areas of storage in the CPU
What are the 5 registers in the CPU?
PC, MAR, MDR, CIR, ACC
What does the Program Counter do?
Holds the ADRESS of the NEXT instruction
What does the Memory Address Register do?
Contains address of RAM to be written to / read from
What does the Memory Data Register do?
Contains the data to be written to RAM / read from RAM
What does the Current Instruction Register do?
Holds the instruction currently being decoded or executed
What does the Accumulator do?
Holds data stored by ALU during operations
What does the Control bus do?
Carries control signals, CU -> CPU
Control signals = [‘read’ or ‘write’]
Carries Control signals, CPU -> RAM
What does the Address Bus do?
Carries addresses ONE WAY
MAR -> RAM
What does the Data Bus do?
Carries data to be written from MAR -> RAM.
When data is read, it carries read data from RAM -> MAR
What is meant by “fetch” in the fetch-decode-execute cycle?
An instruction is taken from RAM -> CPU
What is meant by “decode” in the fetch-decode-execute cycle?
Instruction is decoded by CU
What is meant by “execute” in the fetch-decode-execute cycle?
Instruction is executed, usually by ALU.
