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Post by 87C751 on Jan 1, 2005 18:42:29 GMT -5
Now that I have my second unit spread all over the test bench, initial I/O interface experiments don't look too good. I confirmed that the joystick is coming in on the lower bits of $DC00, but the function buttons aren't tied to any specific CIA ports. I checked $DC00, $DC01, $DD00 and $DD01, but saw no change of state when I closed the switches.
The joystick inputs don't seem usable for outputs, either. I whipped up a little basic prog to turn the data direction register around and then toggle the lines. My voltmeter showed an almost steady 3.2VDC, with occasional flickers to 3.19VDC. Those flickers may have been sync'd with the state transitions, but I don't have an o-scope here to confirm that. In any case, the lines appear to have hard pullups, so I doubt that they'll be usable to effect an SPI interface. Time to formulate plan B.
BTW, this second unit has jumper wires from the 74HC74, like in the photos of Jim's hacked DTV. My first unit doesn't have these jumpers. The second one also shows a bit of the moire pattern I've seen described, and the PS/2 interface seems more prone to the trailing V problem on a powerup. Escaping to keyboard mode on a reset is usually fine.
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Post by NetSamurai on Jan 2, 2005 3:33:56 GMT -5
Well, d**n, that just sucks!
Are you willing to add some hardware to the address/data/control busses? If you use the upper 64K area of RAM, it should remain invisible to normal C64 operations.
I'm sure we will find a way. I have been very busy with the holidays and work, and a bit lazy on top of that. I expect to get back into things shortly. I will keep your question in mind while poking around.
Scott
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Post by 87C751 on Jan 2, 2005 15:48:02 GMT -5
Well, d**n, that just sucks! Are you willing to add some hardware to the address/data/control busses? If you use the upper 64K area of RAM, it should remain invisible to normal C64 operations. Since the easy route seems closed, sure, I'll do the glue. Ideally, I want to stay away from having to sand down the epoxy glob if I can. Not so much because I'm not tooled, but because I eventually want this mod to be available to the Dremel-challenged.
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