Cisco Prisma II Platform Technical References
Prisma II HDTx in the Prisma II
Chassis Not Turning On Technical
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Chassis Not Turning On Technical
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Overview
Purpose
The purpose of this document is to inform Prisma II
™
High Density Transmitter
(HDTx) users of a possible issue about the last HDTx in the Prisma II chassis not
turning on.
Audience
This document is for internal use by Cisco employees only. This document is
written for system engineers and managers, who are responsible for operating
and/or maintaining the Prisma II equipment.
Situation
Cisco has received customer comments regarding issues that the last HDTx would
not turn on after 16or more units were installed in a Prisma II chassis. An analysis
was conducted and the problem appeared to be associated with the chassis ID and
soft start IC.
It was determined that the problem occurred only when the Chassis ID was set to
It was determined that the problem occurred only when the Chassis ID was set to
00 or 01 and the HDTx was inserted into an active rack. The problem probably
will occur with the chassis ID set to any address that contains only one or two “1”
when represented in BCD such as 01, 02, 03, 04, 05, 06, 08, 10, 20, 40, and 80. Refer
to the Group 2 table in Prisma II Chassis ID and Addresses Tables. When the
Chassis ID is set to these numbers, all or all but one or two of the Chassis ID lines
on the backplane are pulled to 5 volts by the pull up resistors on the Chassis ID
select lines in the installed modules. When a new module is plugged into the
rack, the pull up resistors in the new module source the 5 volts from the Chassis
ID lines on to the new module’s 5 volt supply bus which prevents the soft start IC
from starting.