On 4/5/2016 5:31 PM, Rob Clarke wrote: > Hello gentlemen, > > Raising this two year old thread from the dead as I have 3 broken 1551 > paddles and Jim has offered to prototype a 6523T replacement. I've > been doing some investigations into their operation and there were a > few loose ends from the discussion that I thought were worth > commenting on. Yep. I apologize. I wrote all the code, and then it seems I got onto something else and never came back to it. > > 1) The core of the 6523T is indeed a 6525. Using a plus/4, all bits of > all three ports can be set as outputs and will store a written 8-bit > value. Additionally, the control registers R6 and R7 from a 6525 are > present and can be read/written to at FEF6 and FEF7 (assuming set as > device 8). Setting the mode control bit in R6 appears to affect the > usage of port C as expected in the 6525 datasheet. The defined > behaviour of the 6525 on /reset is to set mode control to 0 and > neither FEF6 or FEF7 are accessed by the 264 series ROM, so I would > see no reason to implement them. Good, because adding all that Priority Encoder code will cost a lot of macrocells. Jim Message was sent through the cbm-hackers mailing listReceived on 2016-04-06 00:00:02
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