How 8086 CLK and RESET signals are generated using 8284 ? Explain in detail?

Generating CLK and RESET Signals for 8086 using 8284, The clock and reset signals required for the operation of the 8086 microprocessor. The 8086 microprocessor itself doesn’t include an on-chip clock generator or reset circuitry, so external components are needed to provide these essential signals. The 8284 clock generator chip plays a crucial role in providing the 8086 microprocessor with its timing signals, the clock (CLK) and reset (RESET).

Generating CLK Signals for 8086 using 8284

The 8284 generates the clock signal (CLK) for the 8086 microprocessor. The clock is essential for synchronizing the operation of the microprocessor and other connected devices.

Crystal Oscillator:

The heart of the 8284 is a crystal oscillator. This component vibrates at a precise frequency determined by the attached quartz crystal. The crystal’s inherent properties ensure high accuracy and stability, making it ideal for generating the CPU’s timing reference.

Frequency Divider:

The output of the crystal oscillator is a high-frequency signal unsuitable for the 8086 directly. The 8284 has built-in dividers to reduce this frequency to the desired clock speed for the microprocessor. Typically, the input frequency is divided by three, resulting in a final clock frequency for the 8086.

Clock Generation:

The divided signal from the oscillator drives a clock circuit within the 8284. This circuit generates a square wave signal with a 50% duty cycle and the desired clock frequency. This signal becomes the CLK output of the 8284 and feeds the 8086, synchronizing its internal operations.

Connection to the 8086


The CLK signal generated by the 8284 is connected to the CLK pin of the 8086 microprocessor.

Generating RESET Signals for 8086 using 8284

The 8284 generates the RESET signal for the 8086 microprocessor. The RESET signal is used to initialize the microprocessor and set it to a known state. The 8284. This chip keeps an eye on the power supply and knows when the computer is turned on or off. Whenever the computer is turned on or restarted, the 8284 chip sends a special signal (reset pulse) to the microprocessor, telling it to clear its memory and get ready to start working again.

  • The 8284 includes a reset generator circuit that monitors the power supply and generates a reset pulse when power is applied or restored.
  • The RESET signal is also generated when the microprocessor is initially powered on or when the system is reset.
  • Additionally, the 8284 provides a Manual Reset input (MR), which allows external control of the reset function. When Manual Reset is pulled low, a reset pulse is generated, forcing the 8086 into a known state.

Connection to the 8086


The RESET signal generated by the 8284 is connected to the RESET pin of the 8086.

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