You can use an Amiga-mouse on the VIC20 though, see here: http://sleepingelephant.com/ipw-web/bulletin/bb/viewtopic.php?p=56063#p56063 Am 27.04.2017 um 12:15 schrieb groepaz@gmx.net: > On Thursday 27 April 2017, 01:46:35 Jim Brain <brain@jbrain.com> wrote: >> On 4/27/2017 1:02 AM, groepaz@gmx.net 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! > Message was sent through the cbm-hackers mailing listReceived on 2017-04-27 11:01:26
Archive generated by hypermail 2.2.0.