How Can I Modify The PDP-11's Unibus To Support A Third-party DZ11 Serial Line Unit, Which Requires A Custom Wiring Harness To Interface With The System's Console Interface, While Maintaining Compatibility With The Original RX02 Floppy Disk Controller?

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To modify the PDP-11's Unibus to support a third-party DZ11 serial line unit while maintaining compatibility with the RX02 floppy disk controller, follow these organized steps:

  1. Research and Documentation:

    • Obtain the Unibus specifications to understand signal requirements and device connections.
    • Gather pinouts for both the DZ11 and the PDP-11's console interface (likely using an MMJ connector).

  2. Custom Wiring Harness:

    • Design a wiring harness to adapt the DZ11's connector to the PDP-11's console, ensuring correct alignment of transmit, receive, and ground signals.

  3. Unibus Address Configuration:

    • Determine the RX02's Unibus address to avoid conflicts.
    • Configure the DZ11's address using jumpers, ensuring it does not conflict with the RX02 or other devices.

  4. Interrupt Configuration:

    • Check the interrupt levels used by the DZ11 and RX02.
    • Assign unique interrupts or configure interrupt sharing as necessary to prevent conflicts.

  5. Power Considerations:

    • Verify the power requirements of the DZ11. Ensure the Unibus can supply sufficient power or use an external supply if needed.

  6. Termination Check:

    • Investigate if the Unibus requires termination when adding the DZ11 and implement if necessary.

  7. Physical Installation:

    • Install the DZ11 and wiring harness carefully, grounding yourself to prevent static damage.
    • Route the harness neatly to avoid interference.

  8. Software Configuration:

    • Update the PDP-11's operating system to recognize the new serial lines, possibly involving device drivers or configuration files.

  9. Testing:

    • Boot the system without the new hardware to ensure baseline functionality.
    • Add the DZ11 and test console and floppy disk operations. Check each connection if issues arise.

  10. Community and Resources:

    • Consult forums or communities for advice and troubleshooting tips from similar modifications.

By following these steps, you can successfully integrate the DZ11 while maintaining system compatibility and functionality.