Spi Information Units; Spi Information Unit Overview; Information Unit Transfer Logical Operations - Fujitsu MBA3073 SERIES Technical Manual

1.9

SPI information units

1.9.1

SPI information unit overview

An information unit transfer transfers data in SPI information units. The order in which SPI
information units are transferred within an information unit transfer follows a prescribed sequence.
When information unit transfers are enabled only SPI information units shall be transferred within
the DT DATA OUT phase and DT DATA IN phase.
The SPI information unit sequences shall be as shown in Figure 1.47, 48, 49, 50. See Figure 1.45
and 1-46 for the sequencing rules between the DT DATA IN or DT DATA OUT phases and the
other phases.
The normal progression is from SPI L_Q information unit/SPI command information unit pairs, to
SPI L_Q information unit/SPI data information unit pairs, to SPI L_Q information unit/SPI status
information unit pairs.
Note :
An INIT may request a BUS FREE phase by creating an attention condition and ending a
DISCONNECT message on the corresponding MESSAGE OUT phase. This allows an INIT
to request the TARG break up a long sequence of SPI L_Q information unit/SPI ata
information unit pairs into smaller sequences.
After message phases complete that contain any negotiation (i.e., PPR or WDTR or SDTR) that
results in IU_REQ being changed, the TARG will abort all tasks, except the current task, for the
INIT participating in the negotiation and the INIT shall abort all tasks, except the current task, for
the TARG.
When an information unit transfer agreement is in effect there is no option equivalent to the
"physical disconnect without sending a SAVE DATA POINTERS message." The INIT shall save
the data pointers as soon as the last byte of the last iuCRC for a SPI information unit is transferred.
The save shall occur even if the INIT detects an error in the SPI data information unit.
The TARG will not start a new information unit transfer until all previous REQ(s) have been
responded to by an equal number of ACK(s) except during a sequence of SPI data stream
information units.
1.9.2

Information unit transfer logical operations

SCSI devices using information unit transfers may transfer SPI information units for any number
of I/O processes by using logical connects, logical disconnects, and logical reconnects.
If there is no phase change to a MESSAGE OUT phase or a MESSAGE IN phase then logical
disconnects shall only occur at the completion of:
a) each SPI command information unit;
b) each SPI status information unit;
c) each SPI data information unit;
d) any SPI L_Q information unit if the SPI L_Q information unit DATA LENGTH field is
zero; and
46 C141-C015