Simulator for 8085 microprocessor

 Download GNUSim8085

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Memory mapped I/O and Isolated I/O

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As a CPU needs to communicate with the various memory and input-output devices (I/O) as we know data between the processor and these devices flow with the help of the system bus. There are three ways in which system bus can be allotted to them : Separate set of address, control and data bus to I/O and memory. Have common bus (data and address) for I/O and memory but separate control lines. Have common bus (data, address, and control) for I/O and memory. In first case it is simple because both have different set of address space and instruction but require more buses. Isolated I/O – Then we have Isolated I/O in which we Have common bus(data and address) for I/O and memory but separate read and write control lines for I/O. So when CPU decode instruction then if data is for I/O then it places the address on the address line and set I/O read or write control line on due to which data transfer occurs between CPU and I/O. As the address space of memory and I/O is isolated and the name is so....
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Assignment Questions (Subject:- Microprocessor and Its Interfacing)

Microprocessor and Its Interfacing Assignment Questions   Instructions: ·          Solve any 8 questions in each section. ·          Make appropriate assumptions wherever necessary. Unit – I 1.       What is a microprocessor? What is a flag? Why are the program counter and the stack pointer 16-bit register? 2.       List the major features of 8085 microprocessor. 3.       List the allowed register pairs of 8085. 4.    What is microprocessor? Give the power supply & clock freqency of 8085 5.    List few applications of microprocessor-based system. 6.    What are the functions of an accumulator? 7.    List the 16 – bit registers of 8085 microprocessor. 8.    Define flags? What is the use of ALE? 9.       Explain the need to ...
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Demultiplexing Address/Data Bus AD7- AD0

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Demultiplexing Address/Data Bus AD7- AD0  Pin 30 of 8085 is the ALE pin which stands for ‘Address Latch Enable’. ALE signal is used to demultiplex the lower order address bus (AD0 – AD7). Pins 12 to 19 of 8085 are AD0 – AD7 which is the multiplexed address-data bus. Multiplexing is done to reduce the number of pins of 8085. Lower byte of address (A0 – A7) are available from AD0 – AD7 (pins 12 to 19) during T1 of machine cycle. But the lower byte of address (A0 – A7), along with the upper byte A8 – A15 (pins 21 to 28) must be available during T2 and rest of the machine cycle to access memory location or I/O ports. Now ALE signal goes high at the beginning of T1 of each machine cycle and goes low at the end of T1 and remains low during the rest of the machine cycle. This high to low transition of ALE signal at the end of T1 is used to latch the lower order address byte (A0 – A7) by the latch IC 74LS373, so that the lower byte A0 – A7 is continued to be available till the end of the m...
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