IBM DTLA-305040 Hard Drive Specifications - Page 86

Bit Definitions, DRDY RDY, SERV SRV, CORR COR, Status Register

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9.13 Status Register Status Register 7 6 5 4 3 2 1 0 BSY DRDY DF DSC/ SERV DRQ CORR IDX ERR Figure 72. 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. The use of bit 4 is command dependent. After the DMA Queued commands it is used as SERV. After any other commands are reset, it is used as DSC. 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 zero 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 zero until the Status Register is read by the host, at which time RDY is set back to one. DF Device Fault. DF = 1 indicates that the device has detected a write fault condition. DF is set to zero after the Status Register is read by the host. 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 zero 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. SRV is set to one when the device is ready to transfer data after it releases the bus for execution of a DMA Queued command. 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 zero. IDX Index. IDX=1 once per revolution. Since IDX=1 only for a very short time during each re- volution, the host may not see it set to one 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. Deskstar 40GV & 75GXP hard disk drive specifications 74

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9.13
Status Register
ERR
IDX
CORR
DRQ
DSC/
SERV
DF
DRDY
BSY
0
1
2
3
4
5
6
7
Status Register
Figure 72. 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 acknow-
ledge. Any pending interrupt is cleared whenever this register is read.
If BSY=1, no other bits in the register are valid.
The use of bit 4 is command dependent. After the DMA Queued commands it is used as SERV. After any
other commands are reset, it is used as DSC.
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 zero 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 zero until the
Status Register is read by the host, at which time RDY is set back to one.
DF
Device Fault. DF = 1 indicates that the device has detected a write fault condition. DF is
set to zero after the Status Register is read by the host.
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 zero 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. SRV is set to one when the device is ready to transfer data after it releases the
bus for execution of a DMA Queued command.
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 zero.
IDX
Index. IDX=1 once per revolution. Since IDX=1 only for a very short time during each re-
volution, the host may not see it set to one 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 com-
mand. 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.
Deskstar 40GV & 75GXP hard disk drive specifications
74