Explain the need to demultiplex the bus AD7-AD0 in 8085 microprocessor?

Answer 1

The AD0-AD7 lines in an 8085 are multiplexed to reduce the pin count of the IC. Several added features were added to the 8085 from the 8080 design, and Intel did not want to require a larger package.

Answer 2

The address bus 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.

Answer 3

The AD0-AD7 lines in an 8085 are multiplexed to reduce the pin count of the IC. Several added features were added to the 8085 from the 8080 design, and Intel did not want to require a larger package.

Answer 4

Demultiplexing the bus AD7-AD0 in the 8085 microprocessor is necessary because it allows the processor to access individual address and data lines separately. The 8085 microprocessor has a multiplexed address/data bus, meaning that the same lines are used to carry both address and data information. Demultiplexing separates the address and data signals, enabling the processor to read/write data from/to specific memory locations accurately. This process is crucial for the proper functioning of the microprocessor and ensures efficient communication between the processor and memory devices.

Answer 5

The A0-A7 address bus and the D0-D7 data bus on the 8085 is multiplexed into the AD0-AD7 address/data bus in order to keep the number of pins on the chip to 40. This saved 8 pins and cost 1 pin (ALE), with a net savings of 7 pins.

Answer 6

only if we demultiplex it , it can used as both address bus and data bus(only one at a time) depending upon the state of ALE