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C141-E112-01EN
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• The command is issued in a sequence of the READ LONG or WRITE LONG (to the same
address) command issuance. (WRITE LONG command can be continuously issued after the
READ LONG command.)
If above condition is not satisfied, the command operation is not guaranteed.
At command issuance (I/O registers setting contents)
1F7
H
(CM) 0011001R
1F6
H
(DH)
×
L
×
DV Head No. /LBA [MSB]
1F5
H
(CH)
1F4
H
(CL)
1F3
H
(SN)
1F2
H
(SC)
1F1
H
(FR)
Cylinder No. [MSB] / LBA
Cylinder No. [LSB] / LBA
Sector No. / LBA [LSB]
Number of sectors to be transferred
xx
R = 0 or 1
At command completion (I/O registers contents to be read)
1F7
H
(ST) Status information
1F6
H
(DH)
×
L
×
DV Head No. /LBA [MSB]
1F5
H
(CH)
1F4
H
(CL)
1F3
H
(SN)
1F2
H
(SC)
1F1
H
(ER)
Cylinder No. [MSB] / LBA
Cylinder No. [LSB] / LBA
Sector No. / LBA [LSB]
00 (*1)
Error information
*1 If the command is terminated due to an error, this register indicates 01.
(20) READ BUFFER (X'E4')
The host system can read the current contents of the sector buffer of the device by issuing this
command. Upon receipt of this command, the device sets the BSY bit of Status register and sets
up the sector buffer for a read operation. Then the device sets the DRQ bit of Status register,
clears the BSY bit, and generates an interrupt. After that, the host system can read up to 512 bytes
of data from the buffer.
At command issuance (I/O registers setting contents)
1F7
H
(CM) 11100100
1F6
H
(DH)
×××
DV xx
1F5
H
(CH)
1F4
H
(CL)
1F3
H
(SN)
1F2
H
(SC)
1F1
H
(FR)
xx
xx
xx
xx
xx