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The data and address buses are multiplexed in order to save pin count on the chip. In the first clock cycle of a read or write cycle, the address is emitted on the address/data bus. The ALE signal is used to strobe the address, after which the address/data bus becomes the data bus. External logic is expected to strobe the address at the trailing edge of ALE.
ALE is generated directly by the 8085, and by the 8086/8088 in minimum mode. In maximum mode in the 8086/8088, ALE is generated by the 8288 Bus Controller.
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What Are the Types of Buses in a Computer?
There are 2 kinds Data bus and address bus data bus which carries the data ( includes both instruction and data). address bus which carries where the data in the data bus must be sent to in the RAM or which I/O device has to be active to read / write data to the data bus .
Why is data bus bidirectional but address bus unidirectional?
The address bus is unidirectional becos address information is always given by microprocessor to i/o devices. The data bus is bidirectional bcos it takes the data from other devices & also give the data to other i/o devices
What is an address buffer and a data buffer?
The contents of the stack pointer and program counter are loaded into the address buffer and address-data buffer. These buffers are then used to drive the external address bus and address-data bus. As the memory and I/O chips are connected to these buses, the CPU can exchange desired data to the memory and I/O chips. The address-data buffer is not only connected to the external data bus but also to the internal data bus which consists of 8-bits. The address data buffer can both send and receive data from internal data bus.
Why is data bus bidirectional but address bus is unidirectional?
since data can be read /write from/to the microprocessor, hence data bus is bidirectional. if data is required read from microprocessor then it will be pointing to a memory location by the address bus, by indicating which location data its required to read. similarly to write a data to a location, again the microprocessor will be to that particular location by holding that address in address bus. hence it will be unidirectional.
Difference between data bus and data control bus?
An Address Bus gives the memory instructions on where to place the actual data that it will stored or read. Basically a map location. The Data Bus carries the information that is going to be stored or read using the location that the Address Bus gave to the memory. Address bus is unidirectional while data bus is bi directional
How do you demultiplex address and data bus?
In order to demultiplex the address and data bus, you provide latches that sample the multiplexed bus. At ALE=true, they follow the bus. At ALE=falling edge, they lock onto the last value of the bus. The latches will then become the address bus, while the original bus becomes the data bus.
Size of 8086 address bus?
The 8086/8088 has an internal 20-bit address bus and 16-bit data bus. Externally, the address bus is 20-bits, and the data bus is 16-bits for the 8086 and 8-bits for the 8088.The data bus in the 8086 is 16 bits in size, while the address bus is 20.
Which is more usefull a multiplexer or a demultiplexer?
One is useful without the other. Data that is multiplexed at one end of a communication channel must be demultiplexed at the other end.One is useful without the other. Data that is multiplexed at one end of a communication channel must be demultiplexed at the other end.One is useful without the other. Data that is multiplexed at one end of a communication channel must be demultiplexed at the other end.One is useful without the other. Data that is multiplexed at one end of a communication channel must be demultiplexed at the other end.
Distinguish in between data bus system bus address bus?
A data bus system is a way that mass amounts of information can be transferred to a location. The bus address is the location that this information arrives at.
What is the purpose of an address bus?
The address bus is used by the processor in a computer to locate a piece of data from the RAM (Random Access Memory) that it needs to access. No real data is carried via the address bus, as this is the job of the Data Bus. The pieces of data that the address bus locates are called "addresses" and the address bus transfers "data addresses" to and from the control unit.
Why higher order address bus not multiplexed with data bus of 8085?
The higher order address bus is not multiplexed with data bus of 8085 because that is the way Intel designed the processor. Besides, the data bus is only 8 bits and the address bus is 16 bits. If you were to multiplex the whole address bus on the data bus, you would need two T1 (ALE) states, and that would be excess logic. Back to the original answer - that is simply the way Intel designed the processor.
What is bus in 8085?
there are mainly 3 buses are there in 8085. They are: Address bus :-Used to carry address Data bus :- Used to carry data Control bus :-Used to carry signals such as control and timing signals
