Tandy 1000 SL Technical Reference Manual page 556

BIOS Services
ES:BX
=
pointer to a group of address fields for each track. Each ad-
dress field is made up of 4 bytes. These are C, H, R, and
N,
where:
C
=
tracknumber
H
=
headnumber
R
=
sector number
N
There is one entry for every sector on a given track.
=
the number of bytes per sector
(00
=
128,Ol
=
256,02
=
512,03
=
1024)
Exit Conditions
See the following "Exits From All Calls."
Read Drive Parameters
Return the drive parameters.
Entry Conditions
AH
=
08H
DL
=
drive number (0-2 if Tandy 1000 TL; 0-1 if Tandy
1000 SL)
Exit Conditions
AX
=
0
BH
=
0
CH
=
Maximum usable track number
CL
=
Maximum usable sector number
DH
=
Maximum usable head number
DL
=
Number of diskette drives installed (0-2 if Tandy
1000TL; 0-1 if Tandy 1000
SL)
ES:Dl
=
Pointer to diskette drive parameter table for the
maximum media type supported on the specified
drive