82077AA format less than 128 bytes per sector up to 255 bytes per sector? \ VOGONS

82077AA format less than 128 bytes per sector up to 255 bytes per sector?

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First post, by superfury

Posted on 2020-04-12, 12:45

superfury Offline

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I know that the read/write commands can specify reading or writing 1-255 bytes per sector when 0 is specified as the sector size(in byte 😎.

Now, what I want to know is how the format track command can do this? Can it format sectors with 1-255 bytes/sector?

The command bytes have some "Sector Size" byte in two places (both in the 2nd parameter and the last parameter for each sector on the track). Is there a way for them to format things like 120 bytes/sector or the like? Or any custom value between 0 and 255 bytes/sector?

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Reply 1 of 1, by maxtherabbit

Posted on 2020-04-12, 14:28

maxtherabbit Offline

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No that parameter byte is for the sector code. Arbitrary values not supported.
0=128b
1=256b
2=512b
3=1024b
4=2048b
5=4096b
6=8192b

Setting the sector code to 0 and using the data length parameter on r/w commands to determine sector length is only meant to be used with sectors smaller than 128b, and when it is used the FDC still reads and validates a full 128b sector but only transfers x amount of it

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