Main Clock and PAL Carrier Simulation for Atari 8-bit PAL Computers

This project provides a simulation of the main clock and PAL carrier signals for Atari 8-bit PAL computers. The simulation is based on a schematic developed and tested in a circuit simulation environment.

Overview

The goal of this project is to simulate the generation of a PAL carrier signal and verify the integrity of clock signals for Atari 8-bit PAL computers. The design utilizes common components like flip-flops (74LS74) and a crystal oscillator, as well as discrete components such as resistors, capacitors, and transistors.

Files in the Repository

• schematic.png: A schematic diagram of the circuit.
• simulation.png: Transient analysis of the simulated circuit, showing key signals like OSC, PALCARRIER, and other test points.
• README.md: This documentation file explaining the project.
• INSTALL.md: This documentation file explaining the steps required to add the necessary crystal definitions.
• microcap/: MicroCap simulation files.

Circuit Details

The circuit includes:

1. Crystal Oscillator:

   • A 3.546894 MHz crystal (Y1) is used for generating the primary clock signal (OSC).
   • A second 4.433618 MHz crystal (Y2) is used for generating the PAL carrier signal.

2. Flip-Flops (74LS74):

   • Two flip-flops are configured to divide the frequency and produce stable clock signals at different phases.

3. Passive Filters:

   • RC and LC filters are used to shape the signals and reduce high-frequency noise.

4. Discrete Transistor Amplifiers:

   • Transistors (Q6, Q8) are used to amplify and buffer the signals for stability and drive capability.

5. Test Points:

   • Several test points (TP1, PALCARRIER) are defined to observe and verify signal behavior.

Simulation Results

The simulation demonstrates the following:

• The primary oscillator (OSC) generates a clean signal with minimal jitter.
• The PAL carrier signal (PALCARRIER) is stable and aligns with the expected frequency (4.433618 MHz).
• The output signals have the desired waveform shapes, suitable for further use in Atari 8-bit PAL systems.

Screenshots

• schematic.png: A detailed view of the circuit schematic.
• simulation.png: A transient analysis output showing signal behavior over time.

How to Use

1. Load the schematic into a circuit simulator MicroCap.
2. Run the transient analysis to observe the signal waveforms.

Author

Piotr D. Kaczorowski

License

This project is released under the MIT License. See the LICENSE file for more details.

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If you have any questions or suggestions, feel free to open an issue or submit a pull request!