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Dk'tronics Real Time Clock

1,148 bytes added, 02:02, 7 January 2010
Unknown how the timestamps are stored on disk? The normal AMSDOS filesystem / directory entries don't include timestamps.
 
== Timestamps ==
 
Time stamps - P2DOS and CP/M Plus support time stamps, which are stored in each fourth directory entry.
 
'''This method uses Directory Entries with User Number 31 for Timestamps. Which should be incompatible with AMSDOS, so it is probably NOT used in the CPC. On the CPC, the timestamps <might> be maybe stored in the bootstrap sectors...?'''
 
This entry contains the time stamps for the extents using the previous three directory entries. Note that you really have time stamps for each extent, no matter if it is the first extent of a file or not. The structure of time stamp entries is:
1 byte status 0x21
8 bytes time stamp for third-last directory entry
2 bytes unused
8 bytes time stamp for second-last directory entry
2 bytes unused
8 bytes time stamp for last directory entry
 
A time stamp consists of two dates: Creation and modification date (the latter being recorded when the file is closed). CP/M Plus further allows optionally to record the access instead of creation date as first time stamp.
2 bytes (little-endian) days starting with 1 at 01-01-1978
1 byte hour in BCD format
1 byte minute in BCD format
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