M160 Internet Router Hardware Guide
or sets an alarm. The MCS also relays control messages fromthe Routing
Engine to the router components.
Controlling component power-up and power-down—The MCS controls the
power-up sequence of routercomponents as they start, and powers down
components when their offline buttonsare pressed.
Signaling of mastership—Ina router with more than one host module, the
MCS signals to all router components which host moduleis the master and
which is the standby. It relays the mastership signal for the twoPCGs as well.
Providing SONET/SDH clock source—TheMCS generates a 19.44-MHz
SONET/SDH clock signal, along with a signal that indicates which MCS is the
master SONET/SDH clock generator (if two MCS s are installed).
Clock monitoring—The MCS monitors the PCG systemclock and its
SONET/SDH clock to verify that they are providing the expec ted signal. It
generates an alarm if a clock signal is incorrect.
Control of FPC resets—If theMCS detects errorsin an FPC, it attempts to
reset the FPC. After threeunsuccessful reset attempts, the MCS takes the
FPC offline and informs the Routing Engine. Other FPCs are unaffected,
and system operationcontinues.
MCS Components
Each MCS (shown in Figure 10) has the followingcomponents:
PCI interface—Connects the MCS to t he Routing Engine.
100-Mbps Ethernetswitch—Carries signals and monitoring data between
router components.
19.44-MHz stratum 3 referenceclock—Generates clock signal for SONET/SDH
PICs.
I2C controller—Monitorsthe status of router components.
Three LEDs—IndicateMCS status. There is a blue one labeled MASTER, a green
one labeled OK, and an amber one labeled FAI L. Table8 describes the LED states.
Offline button—Prepares the MCS for removal from the router when pressed.
Extractor clips—Control the locking system that secures the MCS in the chassi s.
26 Host Module