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lines as the equivalent of a backpanel logic plug. The drives does not provide pull up resistors on these lines.
The backpanel is required to provide high and low inputs to the SEL_ID lines per the specifications in table 27
on page 71.
Note.
Table 25 gives AL_PA values for each SEL value. The first entry in the table is SEL_ID 00. The last
entry is SEL_ID 7D. SEL_ID 7E is AL_PA 00 which is not valid for an NL_Port, so is not included in
the table. Also, SEL_ID 7Fh does map to a valid AL_PA; however, this value signals the drive that
physical addresses are not being assigned using the SEL lines and that a "soft" address will be
determined by FC-AL loop initialization.
When the Parallel ESI line is low, the enclosure backpanel logic switches to ESI mode if supported. There are
two modes of ESI, seven bits of enclosure status and a bidirectional mode. ESI support and the mode are
determined by the drive using a discovery process. Refer to the Fibre Channel Interface Manual for a descrip-
tion of ESI operation.
9.5.11.1
Parallel Enclosure Services Interface (ESI)
The parallel ESI line is an output from the drive. This line provides the enclosure with an indication of the
present function of the SEL lines. A high level, the default state, indicates the drive requires address informa-
tion on the SEL lines. A low level indicates the drive is attempting an ESI transfer. The enclosure may not sup-
port ESI on any or all drive locations. It may only support the address function. Support of ESI is discovered by
the drive. Refer to the Fibre Channel Interface Manual for a description of ESI operations.
Cheetah 15K.4 FC Product Manual, Rev. C
69
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