TELCOLINK DT - AccessDSL NTU
User Manual
Version: 2.5
Page 13 of 66
o
xDSL recovered clock (if synchronous mode
is used (“PLL” option at slave side is
off)).
The primary RX clock source for module with E1 interface is:
For Master:
o
E1 2 Mbit transmit clock
(if synchronous mode is used (“PLL” option at master
side is off)) or Internal clock (in case of E1 signal loss);
o
xDSL recovered clock (if plesiochronous mode is used (“PLL” option at master
side is on)) or Internal clock (in case of xDSL signal loss).
For Slave:
o
xDSL recovered clock or Internal clock (in case of xDSL signal loss).
The clock sources are automatically switched by the microcontroller, depending on the actual
signal and clock status, which is updated every 100 ms.
3.2.7.2 Synchronous and plesiochronous operation
Both synchronous and plesiochronous operation modes are possible.
Synchronous operation occurs, when the E1 equipment at one end of the xDSL link uses the
receive clock as transmit clock, as shown below.
In this case “PLL” option must be switched off
on both master and slave sides.
E1 NTU /
LTU
Tx
Rx
2048 kHz Clock
E1 Equipment
xDSL Channel
Tx
Rx
E1 Equipment
E1 NTU /
LTU
Master
Slave
Figure 3-2: Synchronous Operation
Plesiochronous operation occurs, when the E1 equipment at both ends of the xDSL link has its
own clock generator, as shown below. In this case
“PLL” option must be switched on both
master and slave sides.
E1 NTU /
LTU
Tx
Rx
2048 kHz Clock
E1 Equipment
xDSL Channel
Tx
Rx
E1 Equipment
E1 NTU /
LTU
Master
Slave
2048 kHz Clock
Figure 3-3: Plesiochronous Operation
Warning:
Do not configure the E1 interfaces at both ends to use the receive clock as