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Circuit Pack Descriptions
7-6
Issue 1
December 1997
An optical switch on the BBG8/BBG8B SYSCTL circuit pack latch causes a
suspension of controller operations and an "F" to be displayed on the controller
panel display when the latch is pulled. Closing the latch causes a controller reset.
These controls and indicators are discussed in more detail under "User Panel" in
Section 6, "Operations Interfaces."
General Description of Operation
7
The SYSCTL circuit pack provides the majority of the control functions on the
shelf. These include circuit pack monitoring, performance monitoring (PM),
protection switching, and user interfaces.
The SYSCTL, which contains a microprocessor, controls links to all other circuit
packs in the system and links to user interfaces. The processor also provides link
access procedure (LAPD) and LAPD packet data processing to support SONET
section DCC.
Detailed Description of Operation
7
Control Circuitry
7
Processor .
7
Figure 7-3 provides an overall block diagram of the SYSCTL circuit
pack. This processor is the highest level processor in the system.
Memory
7
Program Flash-EPROM .
7
The main program is stored in the flash-EPROM, which
combines the nonvolatility of EPROM with the in-circuit reprogramming ability of
electrically erasable programmable read-only memory (EEPROM). Electrically
Erasable Programmable Read-Only Memory FEPROM allows in-service software
upgrades to be performed locally or remotely without replacing the SYSCTL
circuit pack. Program upgrades of remote DDM-2000 OC-12 shelves can also be
done via the overhead channel from the central office (CO). Of course, software
upgrades may also be accomplished by replacing circuit packs with packs that
have already had software upgrades.
RAM .
7
The main processor's random access memory (RAM) is used to store all
volatile information, such as system alarms, PM information, and parameters for
the main processor's operating system.
EEPROM .
7
All nonvolatile parameters, such as provisioning, are stored in the
EEPROM, which maintains its data indefinitely during a power loss.
