Emerson MVME147 manual Common Command Set And Disk Operation, Notes

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COMMON COMMAND SET AND DISK OPERATION

NOTES:	1.	If the previous attach command was the "old" ATTACH ($08) or the
		"new" ATTACH ($78) and the physical-bytes-per-block is equal to the
		logical-bytes-per-block, the logical block address is taken from the
		user packet byte offset $08.
		If the previous attach command was the "new" ATTACH ($78) and
		the logical-bytes-per-block is a multiple of the physical-bytes-per-
		block, the logical block address is calculated by multiplying the
		starting sector number (byte offset $8) by the logical to physical ratio.
		An example would be logical-bytes-per block = $400, physical-bytes-
		per-block = $200, and the users starting sector number = $600. The
		calculated ratio would be 2, and the new starting sector number
		would be 2 * $600 = $C00.
	2.	If the previous attach command was the "old" ATTACH ($08) or the
		"new" ATTACH ($78) and the physical-bytes-per-block is equal to the

logical-bytes-per-block, the number of sectors is taken from the user packet byte offset $0C.

If the previous attach command was the "new" ATTACH ($78) and the logical-bytes-per-block is a multiple of the physical-bytes-per- block, the transfer length is calculated by multiplying the number of sectors (byte offset $C) by the logical to physical ratio. An example would be logical-bytes-per block = $400, physical-bytes-per-block = $200, and the user number of sectors = $30. The calculated ratio would be 2, and the transfer length would be 2 * $30 = $60.

The information for each page below is used with each format parameter listed in the FORMAT PARAMETER PAGE. The FORMAT command performs the following to a Winchester disk:

Mode sense for FORMAT PARAMETER PAGE 3 current values.

If no illegal request error

Mode sense for page 3 changeable values.

If any of the previous mode sense commands returned a "Illegal Request" error status, this next step is skipped (mode sense and mode select are optional). If the previous commands were successful, a mode select command and parameter list is prepared.

If the attach packet value does not match the mode sense value, and if the changeable value is not zero (some bits are changeable), try to put the attach packet value into the field using the changeable mask.

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