Commodore 64: Burner loader

@DrWatson

Published in 

C64 tape formats

 · 3 years ago

Can be found on...

• Ankh
• Boulderdash
• Chiller
• Cowboy Kidz
• Hyperbiker
• Magic Carpet
• Shadowfire
• Spectipede
• Spy vs Spy
• Star Race
• Geoff Capes
• Hades Nebula
• Mama Llama
• Enigma Force
• Nemesis
• etc...

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Threshold = $0180 (384) clock cycles (TAP byte = $2F).
Bit 0 : $22
Bit 1 : $42
Endianess : Varies per tape.
Pilot Byte : Varies per tape. (*95).
Sync Byte : Varies per tape.

Then...

2 bytes : Start address (LSBF)
2 bytes : End address (LSBF)
n bytes : Data

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Notes:

The loader code itself is stored XOR enciphered in the CBM boot files, the XOR cipher value is $59.

To find what values the loader is using for Pilot,Sync and Endianess you have to decipher the first CBM header. (XOR each byte with $59). Then examine the following bytes inside that (deciphered) header...

 Offset |  Information  
 $0083  |  Endianess. $26=MSbF, $66=LSbF.  
 $0088  |  Pilot Byte. 
 $0093  |  Sync Byte. 

There are sometimes 15 unused pulses after the last data byte.

The 15 unused pulses always(?) hold the pattern.. 001000100010101.
This bit pattern is not interpreted by the loader in any way and the pulses may be safely removed if desired.