Tape routines

From: Marko Mäkelä <msmakela_at_gmail.com>
Date: Wed, 26 Jun 2013 21:34:43 +0300
Message-ID: <20130626183443.GA4173@x220>
On Tue, Jun 25, 2013 at 09:59:08PM +0200, Rhialto wrote:
>I see that, as usual, the tape read/write part is very scarcely 
>commented :-) Even now, nobody understands what's happening apparently.

FWIW, when I developed the C2N232 over 10 years ago, I tried to 
understand the Commodore tape routines using the sparsely commented 
disassembly in a hard copy of Mapping the Commodore 64, by Tim Arnot.

In the end, I wrote the pulse stream receiver routine in the C2N232 and 
worked out the decoder. While doing that, I noticed a lot of jitter in 
the pulse widths produced by the Commodore 64 SAVE statement. I did not 
investigate if it is just the usual interrupt handling jitter (caused by 
having to complete the current instruction first). The Atmel AVR is much 
easier to program, and has nice input-capture and output-compare 
features, creating much cleaner signals in less code. :-)


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Received on 2013-06-26 19:00:06

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