SMART Embedded Computing 6806800V18A, Installation And Use Manual

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Shelf Management Module
AXP1440-C07 Installation and Use (6806800V18A) 149
The default configuration of the shelf managers in the AXP1440-C07 chassis to eliminate
the premature failover of the shelf managers is modified by setting
SWITCHOVER_ON_HANDLE_OPEN to FALSE.
The SWITCHOVER_ON_HANDLE_OPEN term is located in the
/etc/shelfman.conf.sam1500
file.
7.4.2.1 Hardware Redundancy Interface
The hardware redundancy signals of the ShMM-1500R are implemented as follows:

Cross-connected ShMM-1500R present input (PRES_R#) and output (PRES_L#)

Cross-connected ShMM-1500R status 0 input (SHMM_STATUS0_R) and output
(SHMM_STATUS0_L)

Cross-connected redundant ShMM-1500R status 1 input (SHMM_STATUS1_R)
and output (SHMM_STATUS1_L)

Active output (ACTIVE#) that can be used on the ShMM-1500R carrier to enable
interfaces that must be exclusively driven by the active ShMM-1500R

Bi-color status LED
The ACTIVE# signal is intended for use on a carrier and is not connected directly to the
peer ShMM-1500R through the backplane. The cross-connected ShMM-1500R status
signals are asynchronous serial bit streams that are transmitted to the peer-ShMM by the
FPGA and communicate the following information: Health status, Switchover Requests,
PRES_R state, Active state, watchdog timer status, parity and other TBD data. An identical
copy of the bit stream is also sent on the redundant ShMM-1500R status signal. This
information is used by the FPGA to ensure that only one of the two connected ShMM-
1500Rs goes into active mode at a time.
Figure 7-4 on page 150
shows the HRI of the
ShMM-1500R.
As shown in the figure, the ShMM-1500R HRI incorporates a hot-swap buffer (IDT
QuickSwitch), which isolates the interface from the peer ShMM prior to FPGA configuration
or when the ShMM-1500R is powered down. The QuickSwitch device is guaranteed to be
disabled (open) when unpowered and does not have a low impedance path from any of the
signal pins to the power or ground rails. Hence, the device prevents an unpowered
ShMM-1500R from loading down the HRI of the peer ShMM-1500R. It also prevents a
carrier from detecting the ACTIVE# output as a zero; that is, active, during a ShMM-1500R
power cycle or a ShMM-1500R power supply failure.
NOTICE
If the --hook erase option is used during the software update, the
SWITCHOVER_ON_HANDLE_OPEN parameter returns to TRUE, following an
upgrade of the shelf manager’s software. In such a case, you have to again change
the value of SWITCHOVER_ON_HANDLE_OPEN to FALSE manually.