Information Technology Reference
In-Depth Information
Figure 6.4
Typical hard-disk controller settings for the primary and secondary drive
Data register (1F0h)
The data register is a 16-bit register which is used to read/write data from/to the disk.
Error register (1F1h)
The error register is read-only and contains error information relating to the last command.
Its definitions are
7
b
6
b
5
b
4
b
3
b
2
b
1
b
0
NDM
BBK
UNC
MCNID
MCR
ABT
NT0
where
•
BBK -
set to 1 if the sector is bad.
•
UNC -
set to 1 if there is an unrecoverable error.
•
NID - s
et to 1 if mark not found.
•
ABT -
set to 1 if command aborted.
•
NT0 - s
et to 1 if track 0 not found.
•
MC - s
et to 1 identifies that the medium has changed (EIDE only). The EIDE standard
support disks which can be changed while the system is running (such as CD-ROMs, tape
drives, and so on).
•
MCR - s
et to 1 identifies that the medium requires to be changed (EIDE only).
Sector count register (1F2h)
This is a read/write 8-bit register which defines the number of sectors to be read, written or
verified. After each transfer to/from the disk causes the register value to be decremented by
one.
