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4.4.9.1 READ command: COMMAND phase (initiator → target)
The READ command is used by an initiator to request a target for transfer of data. Upon receiving this
command, the target returns scan data to the initiator.
The CDB of this command is shown in the following illustration.
7 6 5 4 3 2 1 0
Operator code X'28'
Logical unit number (Reserved) RelAdr
Data type code
(Reserved)
(MSB)
(LSB)
(MSB)
Transfer length
(LSB)
Control byte
(a)Data type code: Byte 2
Specifies the type of data to be transferred between the initiator and target. This scanner supports
X'00'
(image data) only. If any other value is specified, this scanner returns the following error:
• Status: B'0000l' (CHECK CONDITION)
•• Sense key: X'5' (ILLEGAL REQUEST)
(b) Data type qualifier: Bytes 4 to 5
Identifies each data of the same type. This scanner requires specifying byte 4= X'00' and byte 5 =
window
identifier. If the window identifier specified in byte 5 has not been declared by the DEFINE
WINDOW
PARAMETERS command, this scanner returns the following error:
• Status: B"0000l' (CHECK CONDITION)
• Sense key: X'5' (ILLEGAL REQUEST)
(c) Transfer length (TL): Bytes 6 to 8
Specifies the bytes of storage area that the initiator has allocated for the data to be transferred. If TL
= 0, no data is transferred. This is not assumed an error.
The target does not transfer more data than that which is indicated by Th. This scanner requires that
the transfer length not exceed 64K.
If the actual transfer amount differs from the amount indicated by TL, the target creates the
following status and sense data:
Byte 0
1
2
3
4
5
6
7
8
9
Data type qualifier