Category: <b>disk I/O enhancements</b>
<br>Flags: callout or callback (usually hooked rather than called)<p>
<pre><b>INT 15 - SYSTEM - FORMAT UNIT PERIODIC INTERRUPT (PS ESDI drives only)</b>

	AH = 0Fh
	AL = phase code
	    00h reserved
	    01h surface analysis
	    02h formatting
Return: CF clear if formatting should continue
	CF set if formatting should terminate
Note:	called during ESDI drive formatting after each cylinder is completed
SeeAlso: INT 13/AH=1Ah
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