SCSI Primary Commands - 2.pdf

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T10/1236-D Revision 20 18 July 20017.26 WRITE BUFFER command7.26.1 WRITE BUFFER command introductionThe WRITE BUFFER command (see table 118) is used in conjunction with the READ BUFFER command as adiagnostic function for testing logical unit memory in the target SCSI device and the integrity of the service deliverysubsystem. Additional modes are provided for downloading microcode and for downloading and saving microcode.Table 118 — WRITE BUFFER commandBitByte7 6 5 4 3 2 1 00 OPERATION CODE (3Bh)1 Reserved MODE2 BUFFER ID3 (MSB)4BUFFER OFFSET5 (LSB)6 (MSB)7PARAMETER LIST LENGTH8 (LSB)9 CONTROLThis command shall not alter any medium of the logical unit when the data mode or the combined header and datamode is specified.The function of this command and the meaning of fields within the CDB depend on the contents of the MODE field.The MODE field is defined in table 119.Table 119 — WRITE BUFFER MODE fieldMODE DescriptionImplementationrequirements0000b Write combined header and data Optional0001b Vendor specific Vendor specific0010b Write data Optional0011b Reserved Reserved0100b Download microcode Optional0101b Download microcode and save Optional0110b Download microcode with offsets Optional0111b Download microcode with offsets and save Optional1000b - 1001b Reserved Reserved1010b Echo buffer Optional1011b - 1111b Reserved Reserved164 dpANS SCSI Primary Commands - 2 (SPC-2)
18 July 2001 T10/1236-D Revision 20NOTES37 Modes 0000b and0 001b are not recommended.38 When downloading microcode with buffer offsets, the WRITE BUFFER command mode should be 0110b or0111b.7.26.2 Combined header and data mode (0000b)In this mode, data to be transferred is preceded by a four-byte header. The four-byte header consists of allreserved bytes. The BUFFER ID and the BUFFER OFFSET fields shall be zero. The PARAMETER LIST LENGTH fieldspecifies the maximum number of bytes that shall be transferred from the Data-Out Buffer. This number includesfour bytes of header, so the data length to be stored in the device server’s buffer is parameter list length minus four.The application client should attempt to ensure that the parameter list length is not greater than four plus theBUFFER CAPACITY field value (see 7.13.2) that is returned in the header of the READ BUFFER command (mode0000b). If the parameter list length exceeds the buffer capacity the device server shall return CHECK CONDITIONstatus and shall set the sense key to ILLEGAL REQUEST.7.26.3 Vendor specific mode (0001b)In this mode, the meaning of the BUFFER ID, BUFFER OFFSET, and PARAMETER LIST LENGTH fields are not specified bythis standard.7.26.4 Data mode (0010b)In this mode, the Data-Out Buffer contains buffer data destined for the logical unit. The BUFFER ID field identifies aspecific buffer within the logical unit. The vendor assigns buffer ID codes to buffers within the logical unit. Buffer IDzero shall be supported. If more than one buffer is supported, additional buffer ID codes shall be assigned contiguously,beginning with one. If an unsupported buffer ID code is selected, the device server shall return CHECKCONDITION status and shall set the sense key to ILLEGAL REQUEST with an additional sense code of INVALIDFIELD IN CDB.Data are written to the logical unit buffer starting at the location specified by the BUFFER OFFSET field. The applicationclient should conform to the offset boundary requirements returned in the READ BUFFER descriptor. If thedevice server is unable to accept the specified buffer offset, it shall return CHECK CONDITION status and it shallset the sense key to ILLEGAL REQUEST with an additional sense code of INVALID FIELD IN CDB.The PARAMETER LIST LENGTH field specifies the maximum number of bytes that shall be transferred from theData-Out Buffer to be stored in the specified buffer beginning at the buffer offset. The application client shouldattempt to ensure that the parameter list length plus the buffer offset does not exceed the capacity of the specifiedbuffer. The capacity of the buffer may be determined by the BUFFER CAPACITY field in the READ BUFFERdescriptor. If the BUFFER OFFSET and PARAMETER LIST LENGTH fields specify a transfer in excess of the buffercapacity, the device server shall return CHECK CONDITION status and shall set the sense key to ILLEGALREQUEST with an additional sense code of INVALID FIELD IN CDB.7.26.5 Download microcode mode (0100b)If the logical unit is unable to accept this command because of some device condition, the device server shallterminate each WRITE BUFFER command with this mode (0100b) with a CHECK CONDITION status, a sense keyof ILLEGAL REQUEST, and shall set the additional sense code to COMMAND SEQUENCE ERROR.In this mode, vendor specific microcode or control information shall be transferred to the control memory space ofthe logical unit. After a power-cycle or reset, the device operation shall revert to a vendor specific condition. Themeanings of the BUFFER ID, BUFFER OFFSET, and PARAMETER LIST LENGTH fields are not specified by this standardand are not required to be zero-filled. When the microcode download has completed successfully the devicedpANS SCSI Primary Commands - 2 (SPC-2) 165
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