Shift register shenannigans

Discussion in 'The Projects Forum' started by Kevmeister, Aug 4, 2013.

  1. Kevmeister

    Thread Starter New Member

    Feb 17, 2013
    I am designing an adapter which will enable an Amiga CD32 console to be controlled by a Playstation gamepad.

    In order to do this, I need to understand how the official CD32 controller works so I can simulate it with a PIC.

    I have a schematic which shows how a signal on one of the CD32 console joystick pins goes high to put it into "gamepad mode" as opposed to normal joystick mode.

    This pin is attached to the shift/load pin of an 8-bit parallel-in serial-out shift register.

    My problem is this:

    While the gamepad is in gamepad mode (the duration of the gaming session), the shift/load pin is held high, so the data is constantly shifting. When will it load new data (button presses)?

    I have examined the pin with an oscilloscope and the console never toggles the shift/load pin.

    This has had me scratching my head for over a week now.
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
    The schematics I found show that Load is active (low) when "Pot X (5)" is high.
    Note the the top schematic states, in the lower right-hand corner, that Pot X (5)=Clock in. The schematic belies that.
    I hope you know what "Pot X (5)" means. I don't.