IBM IC35L036UWDY10 Hard Drive Specifications - Page 197

WIDE DATA TRANSFER REQUEST 010203H, 1.3.1 Transfer Width Negotiation started by the Initiator

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10.1.3 WIDE DATA TRANSFER REQUEST (010203H) A pair of WIDE DATA TRANSFER REQUEST messages is exchanged between an initiator and a drive to establish a data transfer width agreement between the two devices. The initiator may initiate a wide data transfer negotiation at any time after the LUN has been identified. The drive initiates a wide data transfer negotiation if the drive has not negotiated with the Initiator since the last time the drive was Reset (Power-on Reset, SCSI Bus Hard Reset, or TARGET RESET message). Drive-initiated negotiation occurs either immediately following the COMMAND phase or immediately following the first reconnection. In either case negotiation occurs before any DATA phase between the drive and the initiator. The drive will negotiate the data transfer width agreement prior to negotiating the synchronous data transfer agreement. If a synchronous data transfer agreement is in effect when a WIDE DATA TRANSFER REQUEST message is received, the drive will reset the synchronous agreement to asynchronous mode. The implied data transfer width agreement remains in effect until the drive is Reset (Power-on Reset, SCSI Bus "hard" Reset, or TARGET RESET message) or a new data transfer width agreement is negotiated. If a Reset occurs, the drive to eight-bit mode. Byte Value Description 0 01H Extended message 1 02H Extended message length 2 03H WIDE DATA TRANSFER REQUEST code 3 E Transfer width exponent Figure 183. Wide Data Transfer Request. E The Transfer Width Exponent (E) is two to the transfer width exponent bytes wide. Valid data transfer widths are 8 bits (E = 00h) and 16 bits (E = 01h). Values of E greater than 01h are reserved. 10.1.3.1 Transfer Width Negotiation started by the Initiator If the Initiator recognizes that negotiation is required and sends a WIDE DATA TRANSFER REQUEST message out, the drive responds by changing to the Message In phase and sending a WIDE DATA TRANSFER REQUEST message in to the Initiator prior to transferring any additional message bytes (or any other Information phase bytes) from the Initiator. This provides an interlock during the data transfer width negotiation. The drive responds to each Initiator requested transfer width exponent as shown in the following table. Initiator Request Ei = 00h Ei > 00h Target Response Et = 00h Et = 01h Target Data Transfer Width 8 Bit 16 Bit Figure 184. Initiator Request/Target Response If, after the Target response above the Initiator asserts the ATN signal and the first message received is either a MESSAGE PARITY ERROR or a MESSAGE REJECT message, the drive negates the data transfer width agreement and goes to 8 bits mode. For the MESSAGE PARITY ERROR case the implied data Ultrastar 146Z10 hard disk drive specifications 181

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10.1.3 WIDE DATA TRANSFER REQUEST (010203H)
A pair of WIDE DATA TRANSFER REQUEST messages is exchanged between an initiator and a drive to
establish a data transfer width agreement between the two devices. The initiator may initiate a wide data
transfer negotiation at any time after the LUN has been identified. The drive initiates a wide data transfer
negotiation if the drive has not negotiated with the Initiator since the last time the drive was Reset
(Power-on Reset, SCSI Bus Hard Reset, or TARGET RESET message).
Drive-initiated negotiation occurs either immediately following the COMMAND phase or immediately fol-
lowing the first reconnection. In either case negotiation occurs before any DATA phase between the drive
and the initiator. The drive will negotiate the data transfer width agreement prior to negotiating the syn-
chronous data transfer agreement. If a synchronous data transfer agreement is in effect when a WIDE
DATA TRANSFER REQUEST message is received, the drive will reset the synchronous
agreement to
asynchronous mode.
The implied data transfer width agreement remains in effect until the drive is Reset (Power-on Reset,
SCSI Bus "hard" Reset, or TARGET RESET message) or a new data transfer width agreement is ne-
gotiated. If a Reset occurs, the drive to eight-bit mode.
Transfer width exponent
E
3
WIDE DATA TRANSFER REQUEST code
03H
2
Extended message length
02H
1
Extended message
01H
0
Description
Value
Byte
Figure 183. Wide Data Transfer Request.
E
The Transfer Width Exponent (E) is two to the transfer width exponent bytes wide. Valid data
transfer widths are 8 bits (E = 00h) and 16 bits (E = 01h). Values of E greater than 01h are
reserved.
10.1.3.1 Transfer Width Negotiation started by the Initiator
If the Initiator recognizes that negotiation is required and sends a WIDE DATA TRANSFER REQUEST
message out, the drive responds by changing to the Message In phase and sending a WIDE DATA
TRANSFER REQUEST message in to the Initiator prior to transferring any additional message bytes (or
any other Information phase bytes) from the Initiator. This provides an interlock during the data transfer
width negotiation.
The drive responds to each Initiator requested transfer width exponent as shown in the following table.
Ei > 00h
Et = 01h
16 Bit
Ei = 00h
Et = 00h
8 Bit
Initiator
Target
Target Data
Request
Response
Transfer Width
Figure 184. Initiator Request/Target Response
If, after the Target response above the Initiator asserts the ATN signal and the first message received is
either a MESSAGE PARITY ERROR or a MESSAGE REJECT message, the drive negates the data trans-
fer width agreement and goes to 8 bits mode. For the MESSAGE PARITY ERROR case the implied data
Ultrastar 146Z10 hard disk drive specifications
181