Hitachi hard disk drive specifications
55
8.12
Status Register
Status Register
7
6
5
4
3
2
1
0
BSY
DRDY
DF
DSC
/SERV
DRQ
CORR
IDX
ERR
Table 27 Status Register
This register contains the device status. The contents of this register are updated whenever an error occurs and
at the completion of each command.
If the host reads this register when an interrupt is pending, it is considered to be the interrupt acknowledge. Any
pending interrupt is cleared whenever this register is read.
If BSY=1, no other bits in the register are valid.
Bit Definitions
BSY
Busy. BSY=1 whenever the device is accessing the registers. The host should not read or
write any registers when BSY=1. If the host reads any register when BSY=1, the contents of
the Status Register will be returned.
DRDY (RDY)
Device Ready. RDY=1 indicates that the device is capable of responding to a command.
RDY will be set to 0 during power on until the device is ready to accept a command. If the
device detects an error while processing a command, RDY is set to 0 until the Status Register
is read by the host, at which time RDY is set back to 1.
DF
Device Fault. This product does not support DF bit. DF bit is always zero.
DSC
Device Seek Complete. DSC=1 indicates that a seek has completed and the device head is
settled over a track. DSC is set to 0 by the device just before a seek begins. When an error
occurs, this bit is not changed until the Status Register is read by the host, at which time the
bit again indicates the current seek complete status.
When the device enters into or is in Standby mode or Sleep mode, this bit is set by device in
spite of not spinning up.
SERV (SRV)
Service. This product does not support SERV bit.
DRQ
Data Request. DRQ=1 indicates that the device is ready to transfer a word or byte of data
between the host and the device. The host should not write the Command register when
DRQ=1.
CORR (COR)
Corrected Data. Always 0.
IDX
Index. IDX=1 once per revolution. Since IDX=1 only for a very short time during each
revolution, the host may not see it set to 1 even if the host is reading the Status Register
continuously. Therefore, the host should not attempt to use IDX for timing purposes.
ERR
Error. ERR=1 indicates that an error occurred during execution of the previous command.
The Error Register should be read to determine the error type. The device sets ERR=0 when
the next command is received from the host.