Command Complete (00); Synchronous Data Transfer Request (01,03,01H) - IBM Ultrastar 36LZX Specifications

10.1.1 COMMAND COMPLETE (00)

The drive sends this message to the initiator to indicate that the execution of a command has been
terminated 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 (01,03,01H)

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 167. Synchronous Data Transfer Request.
A pair of Synchronous Data Transfer Request (SDTR) messages shown in Figure 159 are exchanged
between an Initiator and a Target 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
1. after a Power-on Reset
2. after a SCSI Bus "hard" reset condition
3. after a Bus Device Reset message
In addition a SCSI device may initiate a SDTR message exchange whenever it is appropriate to negoti-
ate 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 re-
ception of data. The drive supports transfer period in the range 50 nSec to 425 nSec in incre-
ments of 25 nSec. In addition to this , when the drive is working in LVD mode, it supports 25
nSec transfer period.
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 63.
If ATN is negated before all bytes of a multiple-byte extended message is received, the drive will go to
BUS FREE to signal a catastrophic error.
Ultrastar 36LZX hard disk drive specifications
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