Hitachi HTS421212H9AT00 - Travelstar 120 GB Hard Drive Specifications page 82

Bit Definitions
BSY Busy. Bit 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 Device Ready. When bit RDY=1 it indicates that the device is capable of responding to a com-
(RDY) mand. Bit RDY will be set to 0 during power on until the device is ready to accept a command.
DF Device Fault. It DF=1 it indicates that the device has detected a write fault condition. Bit DF is set
to 0 after the Status Register is read by the host.
DSC Device Seek Complete. If DSC=1, it indicates that a Seek has completed and the device head is
settled over a track. Bit 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 and at that 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 the drive not spinning up.
DRQ Data Request. Bit 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 Corrected Data. Always 0
IDX IDXIndex. Bit 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 continu-
ously. Therefore the host should not attempt to use IDX bit for timing purposes.
ERR Error. Bit 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 bit ERR=0 when the
next command is received from the host.
Travelstar 4K120 Hard Disk Drive Specification
68