Functional Details, Both Devices
General
The GD16367B/GD16368B chip set pro-
vides transmission of 140 Mbit/s (E4) and
155 Mbit/s (STM-1/OC-3).
Both Optical NRZ signal transmission
and Electrical CMI-coded signal trans-
mission are supported by the internal
selectable CMI-Encoding/Decoding
circuitry.
Selectable 2/4/8 bit system interface is
provided.
140/155 Mbit/s and NRZ/CMI
Clock Frequencies
The VCO tuning range covers the clock
frequencies of 280 MHz to 311 MHz. The
actual clock frequency is determined by
reference clocks and received data.
The 280/311 MHz are used for CMI-oper-
ation. When operating in NRZ-mode the
VCO clock is divided by 2.
NRZ/CMI and Parallel Width
Selection
The devices can operate in different line
and system modes; selected by SEL1,
PW2, and PW1 (See Table 1).
The bit order at the system site is defined
with bit 0 as the first bit transferred (DIN0
for the transmitter and DOU0 for the re-
ceiver).
Line/System Loop Back
Connecting the differential Line Loop sig-
nals and clocks (LLxxx) from GD16368B
to GD16367B allows loop-back of the re-
ceived and recovered line signal, when
LLB is high on both devices. The Line
Loop back is also called remote loop
back.
Connecting the differential System Loop
signals (SLxxx) from GD16367B to
GD16368B allows system loop back,
when SLB is high on both devices. The
System Loop back is also called a local
loop back.
Loop Filters
Both circuits comprise fully integrated
PLL functions for re-timing data at the
transmit site, and for clock and data re-
covery at the receive site.
A passive loop filter consisting of a resis-
tor and a capacitor is used for each de-
vice. The external loop filters are
terminated to VEEA as shown in
Figure 1
(for the transmitter) and
Figure 4
(for the
receiver).
The loop filter values are optimised at the
evaluation board GD90367/368. The op-
timal values depend on the actual appli-
cation. The suggested values in
Figures
1
and
4
can be used as starting point for
the optimisation.
Data Sheet Rev. 14
GD16367B/GD16368B
Page 2 of 14
Mode
SEL1
PW2
PW1
Line Clock
[
Frequency/MHz]
System Clock
[Frequency/MHz]
Used Bits
CMI, 2 bit
0
0
0
280/311
70/78
0 & 1
CMI, 4 bit
0
0
1
280/311
35/39
0...3
CMI, 8 bit
0
1
0
280/311
17/19
0...8
Not valid
0
1
1
-
-
-
NRZ, 2 bit
1
0
0
140/155
70/78
0 & 1
NRZ, 4 bit
1
0
1
140/155
35/39
0...3
NRZ, 8 bit
1
1
0
140/155
17/19
0...8
Not valid
1
1
1
-
-
-
Table 1
NRZ/CMI and parallel width selection. This table is common for both devices.