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T13/2132-D Revision 3 June 23, 2010
48 Working Draft Enhanced Disk Drive - 4 (EDD-4)
8.20 Get Device Parameters (FN 48h)
8.20.1 Overview
This function returns default device parameters. It shall be mandatory regardless of the interface subset that is
supported. Table 22 defines the result buffer. On entry the first word of the result buffer shall be the buffer length
in bytes.
Entry
AH 48h
DL BIOS device number
DS:SI Address of result buffer (see table 22)
Exit
Carry Clear Function completed without error
AH Shall be cleared to zero
DS:SI Address of result buffer (see table 22)
Carry Set Function completed with an error
AH Shall be set to the error code
Table 22 — Result Buffer
Offset Type Description
0 Word The caller shall set this value to the maximum Result Buffer length, in bytes. If the
length of this buffer is less than 30 bytes, this function shall not return the pointer to
Drive Parameter Table (DPT) extension. If the buffer length is 30 or greater on entry, it
shall be set to 30 on exit. If the buffer length is between 26 and 29, it shall be set to 26
on exit. If the buffer length is less than 26 on entry an error shall be returned.
2 Word Information Flags. A value of one in a bit indicates that the feature shall be available. A
value of zero in a bit indicates the feature shall be not available and shall operate in a
manner consistent with the conventional INT 13h interface.
Bit Description
15:8 Reserved
7 BIOS calls INT13h FN 50h to access the device
6 Device geometry shall be set to maximum and no media shall be present
when this bit is set to one
5 Media shall be lockable
4 Device has media change notification
3 Device supports write verify
2 Media shall be removable. Bits 4-6 are not valid if this bit is cleared to zero
1 The geometry returned in bytes 4-15 shall be valid
0 DMA boundary errors are handled transparently
4 DWord Number of default cylinders. The content of this field shall be one greater than the
maximum cylinder number. INT 13h FN 08h shall be used to find the logical number of
cylinders.
8 DWord Number of default heads. The content of this field shall be one greater than the
maximum head number. INT 13h FN 08h shall be used to find the logical number of
heads.
12 DWord Number of default sectors per track. The content of this field shall be the same as the
maximum sector number because sector addresses are 1 based. INT 13h FN 08h shall
be used to find the logical number of sectors per track.