Re: Mark space ratio in 1531 data signal

On 11/12/2019 00:46, Nejat Dilek wrote:
> It's better to call it having much more high frequency content though
> in terms of their harmonic series.

Sure, I am not going to begin to pretend I understand the datasette
analogue audio path to know whether that makes a difference.

However going back to the original point, all it's saying is that is
that the kernal creates 50% duty cycle square waves.

Whether the file being stored is binary or ASCII the recording method
used is the same, involving an encoding method unique to Commodore and
designed to ensure maximum reliability of recording and playback. Each
byte of data or program is encoded by the operating system using pulses
of three distinct audio frequencies. These are: long pulses with a
frequency of 1488 Hz, medium pulses at 1953 Hz and short pulses at 2840
Hz._All these pulses are square waves with a mark space ratio of 1:1_

I pointed out before it's likely easier to use a 50% duty cycle as you
need to wait a period of time and set the output one way, wait a period
of time and set the output the opposite way & it will take up less rom
space if the period you are waiting for is the same in both cases.

If you're asking whether a datasette would be capable of recording a
different duty cycle and reading it back reliably, then maybe it could
(although tape quality and datasette manufacturing variances might have
a impact). The limit of 1->0 transitions per second is the same no
matter the duty cycle, because as you say the zero crossing in one
direction is the only important thing for the cpu. So what would be the
benefit?