1.1.1 Structure and Function of Processor Flashcards
CPU’s job?
cpu processes data and instructions. cpu is where all searching,calculating,sorting and decision making takes place
what does the CU stand for?
Control Unit
function of the CU?
to manage execution of instructions.
controls and monitors hardware
controls input and output of data(so signals go to the right place at the right time)
controls flow of data in CPU
what is used for signal sending ?
buses
what is the ALU responsible for ?
responsible for performing mathematical calculations and logic operations. Also it acts as a gateway to processor
where are results from ALU stored?
accumulator
what is a register ?
a high speed storage area in the CPU used for instruction processing
what are the 5 registers ?
PC MAR MDR CIR ACC
what does CIR stand for ?
current instruction register
role of the PC (program counter)
contains address of the next instruction to be executed
function of MAR
stores memory address from which data will be fetched or sent and stored
function of MDR
stores data being transferred to and from access storage
function of CIR
contains information specifying the instruction tags being or about to be performed
function of ACC
stores ALU calculations
what are buses ?
pathways used to send data around the processor
what are the 3 main buses ?
control
data
address
characteristics of a control bus
it is used by CPU to communicate with other devices and components carrying commands and returning status signals
characteristics of a data bus
carries data/information from one register to the other between the processor and the memory
characteristics of an address bus
carries the address of the memory location being read or written to
what bus would be used between the CPU and main memory when MAR needs the instruction address
address bus
what bus would be used to get the instruction data to MDR from main memory
a data bus
what bus would be used between acc and the main memory after instruction execution
control bus
FETCH
PC holds address of next instruction. Address is copied to MAR Location is sent down address bus and fetch signal is sent by control bus Contents from memory go to processor Contents in MDR and then copied to CIR PC increments by 1
DECODE
CIR contents go to control unit
CU does the decoding.
- it also checks against set of instructions in ROM within CPU
Check is preformed to make sure data is present for current instruction (in MDR)