Den Tue, 10 Dec 2019 16:25:57 +0000 skrev smf <smf_at_null.net>: > > On 10/12/2019 13:17, Jeffrey Birt wrote: > > I don't understand the question. There is only one signal from the > > cassette read head. It gets amplified and 'squared up' to make a > > digital signal out of it. That is it. > > One explanation I've see is that it basically converts + to 1 and - > to 0 (or vice versa). The c64 then has an active low trigger which > detects zero crossing. Correct. > The other is that the tape drive itself is look for zero crossing and > creates a low high pulse when it occurs. Almost. It doesn't create pulses, it just changes the output level according to the signal from the tape. Also it's not a zero crossing detector but a schmidt trigger which means that it has to be a certain higher voltage level for it to make a transition from 0 to 1 than for it to change from 1 to 0. This is what ensures that background noise on a blank tape won't output random data from the Datasette, and also ensures that there won't be any random noise on the output when the signal from the tape changes polarity so slow that any noise (from the tape or interference in general) could interfere with the polarity detection. -- (\_/) Copy the bunny to your mails to help (O.o) him achieve world domination. (> <) Come join the dark side. /_|_\ We have cookies.Received on 2020-05-29 23:51:24
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