Correct Answer - Option 2 : achieve separation of address from data
ALE: (Address Latch Enable):
- It is an active high output signal.
- It indicates that the bits on AD7 - AD0 are address bits
- This signal is used to latch the lower order address from the multiplexed bus and generate a separate set of eight address lines A7 – A0
- It is provided by the microprocessor to latch the address into the 8282 / 8283 address latch.
- It is a high pulse active during T1 of any machine cycle. The T1 state is sufficient enough to latch the address on the multiplexed AD0 - AD15 lines.
- Whenever the processor sends a valid address on the multiplexed lines it also makes the ALE High.
- ALE is never floated.
- ALE is used to demultiplexed/multiplexed data buses and address buses.
Note:
The 8085 microprocessor signals can be classified into various groups, namely:
1. address bus,
2. data bus
3. control bus
4. status signals,
5. externally initiated signals
6. acknowledgement, power and frequency
7. serial I/O signals.