鈥?serial output.
鈥?/div>
Receiver operations:
鈥?serial input
鈥?frame detection
鈥?serial-to-parallel conversion
鈥?4 or 8-bit parallel output.
The RF switch box receives serial clock and data signals
from the transmitter section, the receiver input buffers and
from the clock synthesizer. These signals are routed by
multiplexers to the transmitter section, the transmitter
output, the receiver and to the clock divider, depending on
the status of the control inputs. The switch box also
supports a number of test and loop modes.
Transmitter operation
The transmitter section of the TZA3005H converts
STM1/OC3 or STM4/OC12 byte-serial input data to a
bit-serial output data format. Input data rates of 19.44,
38.88, 77.76 or 155.52 Mbytes/s are converted to an
output data rate of either 155.52 or 622.08 Mbits/s. It also
provides diagnostic loopback (transmitter to receiver), line
loopback (receiver to transmitter) and also loop timing
(transmitter clocked by the receiver clock).
An integral frequency synthesizer, comprising a
phase-locked loop and a divider, can be used to generate
a high-frequency bit clock from an input reference clock
frequency of 19.44, 38.88, 51.84 or 77.76 MHz.
REFSEL1
0
0
1
1
REFSEL0
0
1
0
1
C
LOCK SYNTHESIZER
TZA3005H
The clock synthesizer generates a serial output clock
(TXSCLK) which is phase synchronised with the input
reference clock (REFCLK). The serial output clock is
synthesized from one of four SDH/SONET input reference
clock frequencies and can have a frequency of either
155.52 MHz for STM1/OC3 or 622.08 MHz for
STM4/OC12 selected by the MODE input (see Table 1).
Table 1
Transmitter output clock (TXSCLK)
frequency options
TXSCLK
FREQUENCY
155.52 MHz
622.08 MHz
OPERATING
MODE
STM1/OC3
STM4/OC12
MODE
INPUT
0
1
The frequency of the input reference clock is divided to
obtain a frequency of about 19 MHz which is fed to the
phase detector in the PLL. The appropriate divisor is
selected by control inputs REFSEL0 and REFSEL1 as
shown in Table 2.
Table 2
Reference frequency (REFCLK) options
REFCLK
FREQUENCY
19.44 MHz
38.88 MHz
51.84 MHz
77.76 MHz
To ensure the TXSCLK frequency is accurate enough to
operate in a SONET system, REFCLK must be generated
from a differential PECL crystal oscillator having a
frequency accuracy better than 4.6 ppm for compliance
with
鈥淚TU G.813 (option 1)鈥?
or 20 ppm for
鈥淚TU G.813
(option 2)鈥?
To comply with SONET jitter requirements, the maximum
value specified for reference clock signal jitter must be
guaranteed over the 12 kHz to 1 MHz bandwidth (see
Table 3).
2000 Feb 17
7