Difference between revisions of "FDS file format"

From Nesdev wiki
Jump to: navigation, search
m (link back to Famicom Disk System)
 
(One intermediate revision by one other user not shown)
Line 1: Line 1:
 
'''fwNES''' was an [[NES emulator]] developed by Fan Wan Yang.  Its most lasting contribution to the NES scene was its disk image file format, an image of the Quick Disk media.
 
'''fwNES''' was an [[NES emulator]] developed by Fan Wan Yang.  Its most lasting contribution to the NES scene was its disk image file format, an image of the Quick Disk media.
  
The FDS format (file name suffix <code>.fds</code>) is a way to store [[Famicom Disk System]] disk data. It consists of the following sections, in order:
+
The [[FDS]] format (file name suffix <code>.fds</code>) is a way to store [[Famicom Disk System]] disk data. It consists of the following sections, in order:
 
# Header (16 bytes)
 
# Header (16 bytes)
 
# Disk data (65500 * ''x'' bytes)
 
# Disk data (65500 * ''x'' bytes)
Line 9: Line 9:
 
* 4: Number of disk sides
 
* 4: Number of disk sides
 
* 5-15: Zero filled
 
* 5-15: Zero filled
 +
 +
The disk data follows the [[FDS disk format]], but gaps and CRCs are not included in the .FDS image.
  
 
Note: Most games are an even number of sides. Ports from NROM were one side. No commercial FDS game had an odd number of sides greater than 1.
 
Note: Most games are an even number of sides. Ports from NROM were one side. No commercial FDS game had an odd number of sides greater than 1.
Line 19: Line 21:
  
 
After the last file block, fill a side with all 0 so that exactly 65500 bytes is reached.
 
After the last file block, fill a side with all 0 so that exactly 65500 bytes is reached.
 
Gaps and CRCs are not included in the .FDS image.
 

Latest revision as of 15:55, 16 September 2019

fwNES was an NES emulator developed by Fan Wan Yang. Its most lasting contribution to the NES scene was its disk image file format, an image of the Quick Disk media.

The FDS format (file name suffix .fds) is a way to store Famicom Disk System disk data. It consists of the following sections, in order:

  1. Header (16 bytes)
  2. Disk data (65500 * x bytes)

The format of the header is as follows:

  • 0-3: Constant $46 $44 $53 $1A ("FDS" followed by MS-DOS end-of-file)
  • 4: Number of disk sides
  • 5-15: Zero filled

The disk data follows the FDS disk format, but gaps and CRCs are not included in the .FDS image.

Note: Most games are an even number of sides. Ports from NROM were one side. No commercial FDS game had an odd number of sides greater than 1. Disk sides comes in the following order :

  • Disc 1 Side A
  • Disc 1 Side B
  • Disc 2 Side A
  • Disc 2 Side B
  • etc...

After the last file block, fill a side with all 0 so that exactly 65500 bytes is reached.