Parul Polytechnic Institute

Subject Code : 3330705

Name Of Subject : Microprocessor and assembly language

programming

Name of Unit : Introduction to microprocessor

Topic : Multiplexed address and data bus

Name of Faculty : H.M.Avaiya & N.D.Dhameliya

Name of Students: (i) Parekh Krishna(038)

(ii) Shah Rutu(054)

MICROPROCESSOR ARCHITECTUR AND MICROPROCESSOR SYSTEM

DEMULTIPLEXING MULTIPLEXED ADDRESS/DATA BUS

• The multiplexed address/data bus Ad7-AD0 is used to transfer data and address both.

• In order to perform the read or write operation , the memory device requires to identify memory location which is specified by 16-bit address.

• The higher-order address is available through A15-A8 address lines and lower-order address is available through AD7-AD0.

[ FIG : DE MULTIPLEXING OF MULTIPLEX ED ADDRESS DATA BUS.]

• The lower-order address must be latched as it is required by the memory device and AD7-AD0lines must be made free to transfer data.

• The ALE signal is used to demultiplex AD7-AD0 as shown in figure.

• During initial period of instruction execution ALE goes high and multiplexed address/data bus AD7-AD0contains lower byte of the 16-bit address.

• When ALE goes low, this lower – order address is latched into latch and is made available to the memory device.

• It makes the multiplexed path free for data transfer.

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