CXR Larus 80-100-400
Issue 1, July 2006
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5.1025 (continued)
From the phase data, the processor calculates TIE, MTIE, and slip (193 bit
slip) over an observation interval selected through the 54550 card. Jitter is
calculated over a one-second interval using a 10 Hz high pass filter. The clock
recovery circuit used for jitter measurements acts as a single pole low pass
filter for jitter frequencies above 23 kHz. TIE and MTIE are calculated using a
10 Hz low pass filter.
TIE, MTIE, slip, and jitter information is sent to the 54550 Information
Management Card for storage and later reporting and, if certain thresholds are
exceeded (refer to Table 4-A), the corresponding front panel yellow LED is
turned on. If commanded by the 54550 card, raw phase measurements are
accumulated over the observation interval for later reporting.
5.1026 Microprocessor
The SMC is a microprocessor-controlled monitoring device which measures
DS1/E1 error and performance parameters of up to five DS1/E1 inputs. One
of the five inputs is selected either manually by the front panel MON SELECT
button or by automatic scan at user-controlled intervals through the 54550
card. The selected input number appears on the seven segment display and
its signal is passed to a clock and data recovery circuit.
The microprocessor, data latches, address decoder, random access memory
(RAM), read only memory (ROM), and Memory Management Unit (MMU)
perform all the controlling and communication functions of the card.
A watchdog timer (WDT) provides power on reset and resets the
microprocessor should it lock up.
5.1027 Bit Slip between A and B Clocks
Independent of other measurements, the bit slip between the A and B clocks is
determined and displayed alternately with the number of the input being
monitored. A rotating display shows every bit slip. An excessive slip rate
triggers a major alarm.
5.1028 Clock
Select
A clock select circuit inside the phase detector block selects Clock A, Clock B,
Input A, or Input B as reference for the phase detector.
5.1029 Controls and Indicators
The SMC generates alarm reports via the 54550 Information Management
Card when selected thresholds are exceeded or when the A/B clock slip
exceeds one bit in 30 minutes (major alarm). A continuous high reading
indicates no alarm, a continuous low reading indicates a minor alarm, and a
pulsed output indicates a major alarm.