HP Vectra Technical Reference Manual page 259

On Entry: AH
=
F13_RD_SECTORS (02H)
AL
=
number of sectors to transfer
For hard discs the sector range is 1-128 assuming 512 byte sectors
For flexible discs the following formats are recognized:
Media Sector Range
320KB 1-8
360KB 1-9
1.2MB 1-15
DL
=
device number (Flexible
<
80H Hard disc>
=
80H)
DH
=
head number (0-15 not verified)
CH
=
track/cylinder number (not verified)
For hard discs the high two bits of CL are the MSB of the cylinder number in
CH, making a 10 bit value. The valid range is therefore 0-1023. For the
flexible discs the valid ranges are:
Media Track Range
320KB 0-39
360KB 0-39
1.2MB 0-79
CL
=
sector number (not verified)
For the hard disc the valid value range is 1-17.
For the flexible disc the values in the Sector Range column are also the valid
input values for this parameter.
ES:BX
=
address of data buffer for transfers
On Exit: AH
=
Return Status Code (See table 8.7)
Registers Altered: AX
250 Disc