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Fibre Channel Protocol for SCSI, Fourth Version (FCP-4). Revision 00a. October 30, 2006..pdf
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INCITS T10, Project 1828-D, Revision 00a

10/30/06

An FCP_DL value of zero indicates that no data transfer is expected regardless of the state of the RDDATA and WRDATA bits and that no FCP_XFER_RDY or FCP_DATA IUs shall be transferred.

9.2.2.11 FCP_BIDIRECTIONAL_READ_DL field

For a bidirectional SCSI command, the FCP_BIDIRECTIONAL_READ_DL field contains a count of the maximum number of all bytes to be transferred to the application client buffer in FCP_DATA IU payloads by the SCSI command. The FCP_BIDIRECTIONAL_READ_DL field is the Data-In Buffer Size defined by SAM-3.

An FCP_BIDIRECTIONAL_READ_DL value of zero indicates that no read operation is expected regardless of the state of the RDDATA bit and that no FCP_DATA IUs shall be transferred for read data.

If either RDDATA or WRDATA is set to zero, the FCP_BIDIRECTIONAL_READ_DL field is not included in the FCP_CMND IU payload.

9.3FCP_XFER_RDY IU

9.3.1Overview and format of FCP_XFER_RDY IU

The FCP_XFER_RDY IU indicates that the target FCP_Port is prepared to receive part or all of the data for a write operation. The FCP_XFER_RDY IU contains those parameters of the SAM-3 data delivery service required by the initiator FCP_Port, including the length and beginning relative offset of the FCP_DATA IU that is requested. Since the target FCP_Port has established buffering and caching resources based on the requested data, the initiator FCP_Port shall provide the described data in the requested FCP_DATA IU. The initiator FCP_Port shall be ready to transmit any part or all of the number of bytes indicated in the FCP_DL field if requested.

An FCP_XFER_RDY IU shall be transmitted preceding each write FCP_DATA IU when the WRITE FCP_XFER_RDY DISABLED bit is set to zero by Process Login. If the target FCP_Port and initiator FCP_Port have negotiated write FCP_XFER_RDY disabled, FCP_XFER_RDY IUs shall be transmitted to request each write FCP_DATA IU after the first FCP_DATA IU of the command. The first FCP_DATA IU is transmitted without a preceding FCP_XFER_RDY IU (see 6.3.4).

The first 8 bytes of the FCP_XFER_RDY IU payload are defined in FC-FS-2 for all IUs of category 5, the data descriptor category. The fields defined in FC-FS-2 are given FCP names for use in this standard. The format of the FCP_XFER_RDY IU payload is shown in table 21.

Table 21 - FCP_XFER_RDY IU payload

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bit

 

7

6

5

4

 

3

2

1

0

 

 

Byte

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

(MSB)

 

 

FCP_DATA_RO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3

 

 

 

 

 

 

(LSB)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

 

(MSB)

 

 

FCP_BURST_LEN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

7

 

 

 

 

 

 

(LSB)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8

 

 

 

 

 

Reserved

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

11

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

43

Working Draft, FCP-4