IBM DDRS-39130 - Ultrastar 9.1 GB Hard Drive

9.1.1 COMMAND COMPLETE (00)
The file sends this message to the initiator to indicate that the execution of a command has terminated and
that valid status has been sent to the initiator. After successfully sending this message, the file releases all bus
signals and goes to BUS FREE phase.
9.1.2 SYNCHRONOUS DATA TRANSFER REQUEST (01,03,01H)
Byte Value Description
ÄÄÄÄ ÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄÄÄ
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 126. Synchronous Data Transfer Request.
A pair of Synchronous Data Transfer Request (SDTR) messages shown in Figure 126 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 an 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 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 recep-
tion of data. The file supports transfer period in the range 50 nSec to 425 nSec in increments of
25 nSec. In additon to this , when the file is working on LVD the file supports 25 nSec transfer
period.
REQ/ACK Offset
The ACK/REQ offset(X above) is the maximum number of REQ pulses allowed to be out-
standing before the leading edge of its corresponding ACK pulses is received at the file. A
REQ/ACK offset value of zero indicate asynchronous data transfer mode. The file supports
REQ/ACK offset values in the range 0 through 15.
If ATN is negated before all bytes of a multiple-byte extended message is received, the file will go to BUS
FREE to signal a catastrophic error.
9.1.2.1 Synchronous Negotiation Started by the Initiator
When target respond with REQ/ACK offset value of 0 , the initiator shall use asynchronous data transfer
mode.
164 OEM Spec. of DDRS-3xxxx