Emulex MD21/S2, Техническое руководство

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SCSI Bus Interface
7.2.2.3 Terminator Power (Optional)
The MD21 supports the single-ended SCSI option which provides pin
26 with termination power that has the following characteristics:
Vcc = 4.0 VDC to 5.25 VDC (through diode)
800 milliamps maximum source drive capability
For information on implementing the SCSI termination power option,
see subsection 5.3.2.
7.2.3 SCSI BUS SIGNALS AND TIMING
SCSI bus activities involve one or more of the following SCSI
phases of operation:
• Arbitration Phase
• Selection Phase
• Reselection Phase
• Command Phase
• Data Phase
• Status Phase
• Message Phase
These phases are described in more detail in Subsection 5.1 of the
Emulex SCSI Disk Controller Programming Reference Manual (manual
number MD2352501). When the SCSI bus is not involved in one of the
above phases, it is in the Bus Free Phase. SCSI phase sequencing
is accomplished by asserting or de-asserting the SCSI bus signals;
the signals are described in Subsection 7.2.3.1.
7.2.3.1 SCSI Bus Signals
There are 18 signals on the SCSI bus. Nine signals are control
signals that coordinate transfer of data between SCSI bus host
adapters and controllers; the other nine signals are for an eight-
bit data bus with parity. The signals are listed and described in
Table 7-1.
Interfaces 7