How address decoding is done in Intel 8085 microprocessor?

Answer 1

Address decoding in the Intel 8085 microprocessor is done by latching the 8 bits of the AD0-AD7 bus during the ALE pulse, holding on the falling edge of ALE. After ALE, the latched results become A0-A7, and the AD0-AD7 bus becomes D0-D7.

Answer 2

Address decoding is required in the Intel 8085 because the low order address bus is multiplexed with the data bus. External hardware, a latch, is required to extract the address from the data during ALE time, latching it on the falling edge of ALE. Usually, a passthrough latch is used, in order to improve address setup timing.

Answer 3

There are certain advantages of address decoding. Some of them are:

1. It reduces the number of lines of the original address.

2. It increases the number of address locations .

For example, lets say, we have 3 address lines,

So, we can select 8 various address locations (i.e. 23=8 locations) if address decoding is not used.

But if add these 3 address lines with a 3X8 decoder & then connect 8 output lines of the decoder with another memory blocks, then we can select more than 8 memory locations.