Parul Polytechnic Institute Subject Code : Name Of Subject : Microprocessor and assembly language programming Name of Unit : Introduction to Microprossor Topic : Pin function of 8085 Name of Faculty : H.M.Avaiya & Bhargav Halari

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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