IBM Ultrastar 36LZX, Specifications

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10.1.4 PARALLEL PROTOCOL REQUEST (01,06,04H)
Parallel Protocol Request messages are used to negotiate a synchronous data transfer agreement and a
wide data transfer agreement and to set the protocol options between two SCSI devices.
Protocol Option (DT_REQ Only) 02h 7
Transfer Width Exponent m 6
REQ/ACK Offset X 5
Reserved 00h 4
Transfer period factor (80M/T) 09h 3
Parallel Protocol Request 04h 2
Extended message length 06h 1
Extended message 01h 0
Description Value Byte
Figure 175. Parallel Protocol Request.
REQ/ACK Offset
X The REQ/ACK Offset value is chosen to prevent overflow conditions in the reception buffer of
the device and offset counter and the Target supports maximum offset of 63 (3Fh). A REQ/ACK
Offset value of zero indicates asynchronous data transfer mode and that the Period Factor field
and the Protocol Option field will be ignored.
M The Transfer Wide Exponent field defines the transfer width to be used during DATA IN phases
and DATA OUT phases. The transfer width that is established applies to all logical units on both
SCSI devices. Valid transfer widths are 8 bits (m=00h) and 16 bits (m=01h) if all the protocol
options bits are zero. The only valid transfer width is 16 bits (m=01h) if any of the protocol
options bits are one.
The protocol options bits (IU_REQ, DT_REQ, and QAS_REQ) are used by the originating SCSI device
to indicate the protocol options to be enabled.
IU_RE
Q
DT_RE
Q
QAS_R
EQ
Reserved
0 1 2 3 4 5 6 7
Bit
Figure 176. Bit position table for Byte 7 of Parallel Protocol Request
QAS_REQ (Quick Arbitrate and Select) is not supported. The bit should be zero.
Ultrastar 36LZX hard disk drive specifications
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