
Data Sheet
57
Rev. 1.0, 2005-06-02
OctalLIU
TM
PEF 22508 E
Functional Description
Figure 18
Recovered and Receive Clock Selection
3.7.1
Receive Line Interface
For data input, two different data types are supported (see also Table 12):
Ternary coded signals received at pins RL1 and RL2 from 0 dB downto -43 dB for E1 or downto -36 dB for
T1/J1 ternary interface. The ternary interface is selected if LIM1.DRS is cleared.
Unipolar data (CMI code) on pin ROID received from an optical interface. The optical interface is selected if
LIM1.DRS is set and MR0.RC(1:0) = 01
b.
3.7.2
Receive Line Coding
In E1 applications, HDB3 line code and AMI coding is provided for the data received from the ternary interface. In
T1/J1 mode, B8ZS and AMI code is supported. Selection of the receive line code is done with register bits
MR0.RC(1:0) (MR0). In case of the optical interface the CMI Code (1T2B) with HDB3 or AMI postprocessing is
provided. If CMI code is selected the receive route clock is recovered from the data stream. The CMI decoder does
not correct any errors. The HDB3 code is used along with double violation detection or extended code violation
detection (selectable by MR0.EXZE)). In AMI code all code violations are detected. The detected errors increment
the code violation counter (16 bits length).
The signal at the ternary interface is received at both ends of a transformer.
An overview of the receive line coding is given in Table 12.
3.7.3
Receive Line Termination (Analog Switch)
In general the E1 line impedance operating modes with 75
(used with coaxial cable) or with 120 (used with
twisted pair cable) line termination are selectable by switching resistors in parallel or using special transformers
with different transfer ratios in one package (using center tap). These two options both provide only one analog
front end circuitry for both transmission media types.
The OctalLIU
TM supports a software selectable generic E1/T1/J1 solution without the need for external hardware
changes by using the integrated analog switch and two external resistors for line impedance matching, see
application example in Figure 19. By default the analog switch is off.
This allows, for example, to switch between 100 W (T1/E1 twisted pair) and 75 W (E1 coax) termination resistance
using the external resistors R
E1 = 100 and RE2 = 300 , see Table 13. The analog switch can be controlled by access to the register bit LIM0.RTRS (LIM0) and by hardware using the receive Multi Function Ports. For that, only
SYNC
OctalFALC_rec_clk_sel_2
Receiveclock
selection
to
DCO_R
Recoveredclock
selection
to
DCO_R
channel 1
channel 2
RCLK1
B
A: controlledby CMR5.DRSS(2:0)
B: controlledby GPC(2:6).RS(2:0)
to
DCO_R
channel 4
C
RCLK
...
RCLK7
RCLK4
RCLK5
RCLK8
RCLK6
RCLK3
RCLK2
A
pins
Recoveredclock
selection
Recoveredclock
selection