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Added some documentation of the intention here.

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Thomas Harte 2016-08-19 11:04:59 -04:00
parent 4edd1214f1
commit 73ce67bee8
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Storage/Tape/Formats/TapePRG.cpp
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@ -8,6 +8,42 @@
#include "TapePRG.hpp"
/*
My interpretation of Commodore's tape format is such that a PRG is encoded as:
[long block of lead-in tone]
[short block of lead-in tone]
[count down][header; 192 bytes fixed length]
[short block of lead-in tone]
[count down][copy of header; 192 bytes fixed length]
[gap]
[short block of lead-in tone]
[count down][data; length as in file]
[short block of lead-in tone]
[count down][copy of data]
... and repeat ...
Individual bytes are composed of:
word marker
least significant bit
...
most significant bit
parity bit
Both the header and data blocks additionally end with an end-of-block marker.
Encoding is via square-wave cycles of four lengths, in ascending order: lead-in, zero, one, marker.
Lead-in tone is always just repetitions of the lead-in wave.
A word marker is a marker wave followed by a one wave.
An end-of-block marker is a marker wave followed by a zero wave.
A zero bit is a zero wave followed by a one wave.
A one bit is a one wave followed by a zero wave.
Parity is 1 if there are an even number of bits in the byte; 0 otherwise.
*/
#include <sys/stat.h>
using namespace Storage;