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Host Interface
4-12 C156-E205-01EN
The ODD sets BSY:
a) After RESET- is negated or within 400 ns of setting the SRST bit of the
Device Control Register
b) Within 400 ns of receiving a command when the DRQ bit is not set
c) Between data transfer blocks of the PIO data-in/PIO data-out command
when the DRQ bit is not set
d) After data block transfer with the PIO data-out command when the DRQ
bit is not set
e) During DMA transfer when the DRQ bit is not set
In all other cases, the ODD does not set BSY.
If BSY is set after RESET- is negated, the SRST bit is set, or a Device Reset
command is issued, it remains set until the ODD completes the internal reset
process.
!
DRDY (Device Ready) is always 1, except at the time after reset is made until
the next command is issued.
!
For SERV, set the same value as that of DRDY. The SERV bit should be
ignored from the standpoint of compatibility.
!
DRQ (Data Request) indicates that the ODD can transfer one byte or one
word to or from the host. When DRQ is 1, the ATAPI Interrupt Reason
register of the current packet command is effective.
!
CHK indicates that an error occurred in command processing. The Error
register contains additional information on the cause of the error. When the
ODD sets CHK to 1, the items below are not changed until a new command is
received or the ODD is reset.
"
CHK bit of the Status register
"
Error register
"
Device/Head register