On Thursday 27 April 2017, 01:46:35 Jim Brain <email@example.com> wrote: > On 4/27/2017 1:02 AM, firstname.lastname@example.org wrote: > > mmmh there must be something else that is different - if that'd be the > > only > > difference the 1351 should still produce *some* values, right? > > Since I didn't want to promote bad information, I fired up the scope. > > It looks like it uses the same 512 cycles (506uS per ADC cycle, > according to my NTSC VIC-20), but holds the line low only for 64uS, and > then releases the line for the remaining 448uS. > > The 64, on the other hand, drags the line low for 256 cycles, and then > releases it for 256 cycles. > > The mouse operates by taking the value it wishes to send, adds 256 to > it, waits for that falling edge of POTX, waits that many 1uS cycles, and > then pulls the line high. Lather, rinse, repeat. > > The ADC has to start sampling the comparator immediately after it > releases the line. Assuming the VIC samples 256 cycles, it must > sample from 64uS to 319uS, while the 64 samples from 256 to 511uS. Of > the 64 256-511uS, the 1351 only starts pulling the line hi at 256+64uS = > 320uS. Thus, the 1351 never pulls the line high at any time the VIC-20 > ADCs are scanning the line. aaah i see. that makes sense. thank you! -- http://www.hitmen-console.org http://magicdisk.untergrund.net http://www.pokefinder.org http://ar.pokefinder.org Usability:Simplify the Solution Design:Simplify the Problem Message was sent through the cbm-hackers mailing listReceived on 2017-04-27 11:00:03
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