IBM IC35L036UWDY10 Hard Drive Specifications - Page 198

transfer width agreement is reinstated if the drive successfully retransmits the WIDE DATA TRANSFER REQUEST message to the Initiator. For any other message the drive completes negotiation and goes to the negotiated data transfer width. 10.1.3.2 Transfer Width Negotiation started by the drive If the drive recognizes that negotiation is required, it sends a WIDE DATA TRANSFER REQUEST message to the Initiator with the transfer width exponent equal to 1 (E = 01h). The Initiator must respond by asserting the ATN signal prior to its release of ACK for the REQ/ACK handshake of the last byte of the WIDE DATA TRANSFER REQUEST message. This provides an interlock during the wide data transfer negotiation. If the Initiator does not assert the ATN signal, the drive goes to 8 bit mode. If the Initiator asserts the ATN signal, the drive changes to the MESSAGE OUT phase and receives a message from the initiator. If the first message received is a WIDE DATA TRANSFER REQUEST message, the Target establishes the new data transfer mode. The Target interprets the Initiator corresponding transfer width exponent as shown in the following table. Initiator Request Ei = 00h Ei = 01h Ei > 01h Target Data Transfer Width 8 Bit 16 Bit (8 Bit) Figure 185. Target Request to Initiator If the first message received from the Initiator is either a MESSAGE PARITY ERROR or a MESSAGE REJECT message, the drive goes to 8 bit data transfer mode. In the case of a MESSAGE PARITY ERROR, the wide data transfer negotiation is restarted if the drive successfully retransmits the WIDE DATA TRANSFER REQUEST message to the Initiator. If the first message received from the Initiator is any other message, the Target goes to 8 bit data transfer mode. The Target assumes that the Initiator does not support wide data transfer and does not attempt to renegotiate with this Initiator. The implied agreement for wide data transfer operation is not considered to exist by the Target until the Target leaves the MESSAGE OUT phase, implying that no parity error was detected. If the Target detects a parity error while attempting to receive the message from the Initiator, the Target goes to 8 bit data transfer mode. The Target will attempt to resume the wide data transfer negotiation by retrying the MESSAGE OUT phase. Note: If during the MESSAGE IN phase of negotiations (either Target or Initiator started) ATN is asserted prior to transmission of the last byte of the message and the message is not MESSAGE PARITY ERROR or MESSAGE REJECT, the drive goes to 8-bit data transfer mode. Ultrastar 146Z10 hard disk drive specifications 182