Task Complete (00H); Synchronous Data Transfer Request (010301H); Figure 178. Synchronous Data Transfer Request - IBM IC35L036UWDY10 - Ultrastar 36.7 GB Hard Drive Specifications

If an unsupported message is received, the drive will send the MESSAGE REJECT message to the initi-
ator. If at the time the unsupported message is received a valid nexus exists, the drive will continue with
the command. If no valid nexus exists, the drive will go to BUS FREE.

10.1.1 TASK COMPLETE (00h)

The drive sends this message to the initiator to indicate that the execution of a command has been termi-
nated and that valid status has been sent to the initiator. After successfully sending this message the drive
releases all bus signals and goes to BUS FREE phase.

10.1.2 SYNCHRONOUS DATA TRANSFER REQUEST (010301H)

Byte Value Description
0 01H Extended message
1 03H Extended message length
2 01H SYNCHRONOUS DATA TRANSFER REQUEST code
3 M Transfer period (M times 4 nanoseconds)
4 X REQ/ACK offset

Figure 178. Synchronous Data Transfer Request .

A pair of SYNCHRONOUS DATA TRANSFER REQUEST (SDTR) messages shown in Figure are
exchanged between an initiator and a drive to establish the synchronous data transfer mode between the
two devices. The message exchange establishes the permissible transfer period and REQ/ACK offset for
a synchronous data transfer between the two devices. The initiator may initiate a synchronous data
transfer negotiation at any time after the LUN has been identified. A SYNCHRONOUS DATA TRANSFER
REQUEST (SDTR) message exchange shall be initiated by a SCSI device whenever a previously
arranged data transfer agreement may have become invalid. The agreement becomes invalid after any
condition which may leave the data transfer agreement in an indeterminate state such as after
! a Power-on Reset
! a SCSI Bus Reset condition
! a Target Reset message
In addition a SCSI device may initiate a SDTR message exchange whenever it is appropriate to negotiate
a new data transfer agreement (either synchronous or asynchronous).
M The transfer period (M above) is the minimum time allowed between leading edges of successive
REQ pulses and of successive ACK pulses to meet the device requirements for successful
reception of data. The drive supports transfer period of 50, 100, and 200 ns. In addition to this,
when the drive is working in LVD mode, it supports 25 ns transfer periods.
REQ/ACK Offset
X The ACK/REQ offset (X above) is the maximum number of REQ pulses allowed to be outstanding
before the leading edge of its corresponding ACK pulses is received at the drive. A REQ/ACK
offset value of zero indicates asynchronous data transfer mode. The drive supports REQ/ACK
offset values in the range 0 through 127.
If ATN is negated before all bytes of a multiple-byte extended message are received, the drive will go to
BUS FREE to signal a catastrophic error.
Ultrastar 146Z10 hard disk drive specifications
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