Explain how to de-multiplex address from multiplex address / data line
Answers
has 8 signal lines A8-A15. They are unidirectional. The other 8 address bits
are multiplexed with the 8 data bits. Therefore the bits AD0-AD7 are
bi-directional. They serve as A0-A7 and D0-D7 at the same time. As AD7-AD0
lines serve a dual purpose they have to be demultiplexed to get all the
information.
The address's
high order bits remain on the bus for 3 clock periods. The low order bits
remain for only 1 clock period and may be lost if they are not saved
externally. An external latch is used to save the value of AD7-AD0 when it is carrying the address bits so that the entire address remains for the 3 clock cycles.
After ringing the doorbell of Mrs. Dorling who lived at Number 46, Marconi Street, the protagonist was given a cold reception and Mrs Dorling took much time to recognize her. Mrs Dorling had thought everyone in the protanogist’s family was dead and asked if anyone else had come along with her. Mrs Dorling refused to let the protagonist inside her home and told her to come back sometime later. The protagonist recognized her mother’s green cardigan which Mrs Dorling was wearing. She decided to go back to the train station and thought about her mother and how she told her about Mrs. Dorling who was an acquaintance of hers. During the war, Mrs Dorling would visit their house and take their possessions with her as she didn’t want them to get lost if they ever left the place. Mrs. Dorling had a broad back.
The protagonist decided to go to Mrs Dorling’s home to get back their belongings. When she rang the bell, Mrs. Dorling’s daughter answered the door. She let her in and asked her to wait in the living room. When they were crossing the passage, the protagonist noticed their Hanukkah candle stand that they had never used because it had been unmanageable. When she reached the living room, she was horrified as she saw all her mother’s things that were arranged in a tasteless manner. The furniture was ugly and the room had a muggy smell and it made her disinterested and she wanted to leave the place. Mrs. Dorling’s daughter offered her a cup of tea and the protagonist noticed the old table cloth that had a burn mark on it. When the girl was showing her the silver fork and spoons that actually belonged to the protagonist, she jumped up and walked out of the house. She decided not to visit the place again as it brought back memories of the past and hence, she decided to forget the address.