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Old 21 September 2014, 03:44   #1
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A600 and ghost keystrokes

Out of curiosity, what might cause A600 to produce keystrokes even when the keyboard is not physically attached? Sequences of keystrokes appear randomly every now and then Again some caps issue?
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Old 21 September 2014, 05:30   #2
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Most likely if the keyboard doesn't work and it's producing strange chars its u13 keyboard mpu or u7 via.

If you had an oscilloscope I would look at pin 41 and 42 of u13 and see if the keyboard mpu was producing junk.

Check R511b or R511a are present on the board and the right value if they got knocked off the keyboard clock and data lines would be flapping in the breeze and could produce garbage.
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Old 21 September 2014, 05:40   #3
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When I had that problem on the commodore 64 the culprit was CIA chip, but also certain joystick (IIRC autofire joystick) produced keystrokes. don't know if amiga works in the same way of the c64
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Old 21 September 2014, 08:24   #4
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The Amiga does not work in the same way. I'm giving my vote to the keyboard MPU.
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Old 21 September 2014, 11:57   #5
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Yes, I can confirm what Jope said, joysticks can emit spurious keyboard input on C64, but not Amiga.
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Old 21 September 2014, 23:10   #6
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Thanks for suggestions!
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