NEC PC-6001A Cassette WAV file issues...
Posted: Wed Jul 12, 2017 1:59 am
I finally got my hands on a PC-6001A and after some repairs I have been trying to load some Z88DK generated code on it. Most emulators work with the cassette format which is a byte stream, but lacks some components of what would be in a WAV file for example. I've studied the nec.c and it seems to suggest that repeated zeros are part of the process, and has some code during WAV file generation that tests for this condition although I'm not sure why the code is doing what it is doing. Studying some of the cp6 files shows that there are places where they are streams of zeros and I have to presume that the CLOAD command loads these properly and continues. My theory is that it takes both zeros AND a steam of raw 1 bits to tell it to stop loading. You don't see these raw 1 bits in the CAS file because they are not a proper frame which begins with a 0, then 8 bits, then 1 and 1 for 2 stop bits.
The problem is that there can be a sequence of three zero's in the prefix_p6 - when this occurs, it will INSERT another "break" of all 1's. Because it is three zeros that triggers this, it ends the load. There was a warning under default: that said problems but it is disabled.
What is the point of doing this? I would think it would be better to just send everything and avoid doing an all 1's break until the end?
The problem is that there can be a sequence of three zero's in the prefix_p6 - when this occurs, it will INSERT another "break" of all 1's. Because it is three zeros that triggers this, it ends the load. There was a warning under default: that said problems but it is disabled.
What is the point of doing this? I would think it would be better to just send everything and avoid doing an all 1's break until the end?