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ZX Interface 1: Difference between revisions
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→Microdrive Data Storage Format
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There is also a final byte clearly visible at 0xFH, which would make the 16th byte, however this is a wasted byte and does not support anything. It may well be used for a 16bit checksum in the future. | There is also a final byte clearly visible at 0xFH, which would make the 16th byte, however this is a wasted byte and does not support anything. It may well be used for a 16bit checksum in the future. | ||
=== Sector Data === | |||
Data files, or "Records" follow each Sector Header file. These are 528 bytes long, and include the same synchronisation pulses at the start as the Sector Header. In addition, while the DATA content of the record is 512 bytes, some spectrum files have a header that parallels the tape header, though obviously omits the filename as that's contained within the record preamble. As such this data stream contains; | |||
12 bytes ( 6 per channel ) of synchronisation pulses ( possibly with some spurious additional pulses ) | |||
15 bytes of Preamble, containing the filename, record number and Received Flags. | |||
512 bytes of record data and; | |||
1 wasted byte ( that also might be used for a 16 bit checksum in the future ) | |||
[[File:Sector record file example.png]] | |||
In this example, it can be seen that the identifier section ( preamble ) is very similar to the format of the Sector Header identifier section. The same routines read both in the Interface 1 ROM. | |||
{| class="wikitable" style="text-align: center;" | |||
|- | |||
| Offset || Example Byte || Significance | |||
|- | |||
| 00H || 0x01 || This is the RECFLG byte. Bit0 signifies a sector header. | |||
|- | |||
| 01H || 0x82 || Sector 0x82. Sectors count from 0xFF to 0x00. Sector 130 in decimal. | |||
|- | |||
| 02H || 0xEB || Undefined. Not in use at the present time. | |||
|- | |||
| 03H || 0x20 || Undefined. Not in use at the present time. | |||
|- | |||
| 04H-0DH || 0x4D, 0x69, 0x63, 0x72, 0x6F, 0x64, 0x72, 0x69, 0x76, 0x65 || Cartridge name, in this case, the cartridge was formatted with ''FORMAT "M";1;"Microdrive"'' Any unused name spaces are padded with 0x20 | |||
|- | |||
| 0EH || 0xA7 || The Sector Header Checksum... | |||
|- | |||
|} | |||
== External links == | == External links == | ||