CXR Larus 80-100-400
Issue 1, July 2006
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1. The primary reference for the A track and hold card is DS1/E1 Input A
and for the B track and hold card it is DS1/E1 Input B.
2. The 54593 can select Input B to be from Input Card A by activating the
CLKSEL output line.
Input references can only be changed by commands from a terminal as
described in the STS 54500 User Manual, Volume 3 (TL1/ITL1) or Volume
4 (Menu).
5.9212 DS1/E1
Receiver
The DS1/E1 receiver regenerates the selected incoming signals and recovers
both the clock and the data. The data go to the framing circuit.
5.9213 Framer
The 54593 communicates with a CS2180 Transceiver Chip for the T1 inputs or
a CS2181 for the E1 inputs. The framing circuit detects the following framing
errors:
a. Yellow Alarm, LOS (175 ±75 consecutive zeros)
b. BPVs
c. Invalid CRC6 codes (ESF framing only) or CRC4 codes (CRC4 framing
only)
An impaired signal causes the microcontroller to cease tracking, go into the
HOLD mode, and show the type of impairment on the seven segment display.
5.9214 Rubidium Oscillator
The 50.255 MHz rubidium oscillator output is divided by five to provide a 10.051
MHz signal to a 48-bit DDFS.
5.9215 Direct Digital Frequency Synthesizer
The oscillator is coupled to the DDFS and acts as a reference for it. The DDFS
operates on the presumption that oscillator frequency is kept within a
reasonable degree of precision, e.g. within one part in 10
-9
. The DDFS uses a
digital process to convert the oscillator signal into a signal having a second
related frequency. The DDFS accomplishes this conversion by utilizing a
stored algorithm and a numerical input from the microcontroller.
The DDFS accepts an integer, N, from the microcontroller. The DDFS then
generates a new output frequency 'F out' from 'F osc' according to the following
formula:
(N) (F osc)
F out =
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