What is Intel 8085 Microprocessor

What is Microprocessor ?

Microprocessor is a programmable, multipurpose, clock driven electronics device. It takes some input and process it according to present program and give a suitable output.

Sometimes Microprocessor is also called CPU(Central Processing Unit).

Microprocessor consists of an ALU, register array, and a control unit. ALU performs arithmetical and logical operations on the data received from the memory or an input device. Register array consists of registers identified by letters like B, C, D, E, H, L and accumulator. The control unit controls the flow of data and instructions within the computer.

Block diagram of Microprocessor
Block Diagram of Basic Microprocessor

Intel 8085 Microprocessor

Intel 8085 Microprocessor is a programmable, multipurpose, clock driven electronics device which contains 246 commands inside it.

It has following properties :

  • It is a 40 pin DIP IC Package.
  • It contains 8 data line and 16 address line.
  • It contains 6500 transistors inside it.
  • Its Clock speed is 3MHz to 6 MHz
  • It could execute 7 lacks 69 thousand instructions per second.
  • Memory Capacity of 8085 Microprocessor is 64KB.
  • This Microprocessor is made by P-Mos technology.
Pin Diagram of Intel 8085 Microprocessor
Pin diagram of intel 8085
Pin Diagram Intel 8985
Pin Descriptions of Intel 8085 Microprocessor
  • Pin no. – 1,2 [X1, X2]
    • The main work of these pins are to generate clock signal with frequency 3MHz to 6Hz.
  • Pin no. – 3 [RESET OUT]
    • It is an output signal.
    • This is given by microprocessor to reset the peripheral devices connected with microprocessor.
  • Pin no. -4,5 [SOD, SID]
    • SOD stands for serial output data. It is used to transfer serial data by microprocessor to other peripheral devices.
    • SID stands for serial input data. It is used to transfer serial data by peripheral devices to microprocessor.
  • Pin no. -6 to 10 [Trap, RST 7.5, RST 6.5, RST 5.5, INTR]
    • These pins are input pin.
    • These pins used to stop the current running program for a short duration of time.
    • Here Trap has highest priority.
    • RST 7.5 has 2nd priority, RST 6.5 has 3rd priority, RST 5.5 has 4th priority and INTR is the last priority.
  • Pin no. – 11 [INTA]
    • INTA stands for interrupt acknowledgement.
    • This is a output pin. This signal is send by microprocessor after receiving the interrupt signal.
  • Pin no. – 12 to 19 [AD0 to AD7]
    • AD0 to AD7 is time multiplexed address and data signal.
    • Here address signal(A0- A7 ) are output signal and D0 to D7 are input signal.
    • AD0 to AD7 are called bidirectional signal.
  • Pin no. – 21 to 28 [A8 to A15]
    • It is a higher order address line.
    • These are output signal.
  • Pin no. – 29,33 [S0, S1]
    • These are called status signal and these are output signal.
    • These signal are used to indicate the internal status of microprocessor they are given billow-
S0S1Operation
00Halt
01Read
10Write
11Fetch
  • Pin no. – 30 [ALE]
    • It is an output pin.
    • This pin is used to separate the time multiplexed address and data signal [AD0 – AD7].
  • Pin no. – 31 [WR]
    • WR is a write signal.
    • WR signal given by microprocessor to other peripheral devices
    • With the help of this signal data are transferred from microprocessor to other peripheral devices.
  • Pin no. – 32[RD]
    • RD is a read signal.
    • RD signal given by microprocessor to other peripheral devices.
    • With the help of this signal data are transferred from peripheral devices to microprocessor.
  • Pin no. – 34 [IO/M]
    • It is an output signal.
    • IO/M stands for input output/memory.
    • If IO/M =0 then microprocessor communicate with memory and if IO/M = 1 the microprocessor communicate with I/O devices.
  • Pin no. – 35 [Ready]
    • It is an input signal.
    • This signal is given by peripheral devices to microprocessor to communicate the data if processor is not busy then ready signal accepted by microprocessor otherwise not accepted.
  • Pin no. – 36 [RESET IN]
    • It is an input signal.
    • It is a low priority signal.
    • This signal is given by peripheral devices to microprocessor to reset the internal section of microprocessor.
  • Pin no. – 37 [Clock Out]
    • It is an output pin.
    • This pin is used to provide clock signal by microprocessor to peripheral devices connected with microprocessor.
  • Pin no. – 38 [HLDA]
    • It is an output signal.
    • This signal is send by microprocessor after receiving HOLD signal.
  • Pin no. – 39 [Hold]
    • It is an input pin.
    • This signal given by peripherals devices to take control the bus present in microprocessor.

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