Re: Mark space ratio in 1531 data signal

From: Marko Mäkelä <*msmakela_at_gmail.com*> Date: Tue, 10 Dec 2019 17:15:14 +0200 Message-ID: <20191210151514.GA2952830_at_jyty> · msmakela_at_gmail.com

On Tue, Dec 10, 2019 at 04:00:55PM +0100, Mia Magnusson wrote:
>>For writing the tape head is driven to saturation or not. It is not 
>>very complicated.
>
>Rather saturation in either polarity.

A 50% mark/space ratio might have the benefit that it is immune to any 
change of signal polarity.

The 264 series machines wire CASS READ to a level-sensitive I/O pin, 
while all others (PET, Vic-20, C64, C128, CBM II) connect it to 
something that detects a falling edge. So, only for the 264 series it 
might matter which polarity is used. In reality, the 264 series uses an 
even slower encoding (and slightly different high-level format) than the 
other machines. See the source code of my C2N232 firmware and related 
software (c2nload, c2n) for more details.

	Marko