Installation guide

LTU/NTU SZ-DOC-W5-1.pd
f
Operating Manual
V
ersion: 1.5
Revision: 2002-09-10 22
3.4.8 Clock Polarity
In X.21 mode the sampling instant for the incoming data stream on circuit T of the user interface
(UIF) can be switched to rising or falling slope of the contradirectional clock circuit S.
Data transitions of the received data on UIF circuit R is not influenced by this setting.
In default configuration "normal" circuit T is sampled on rising edge of clock S. The data
transitions on T and R shall occur at the OFF to ON transition of S (according X.24 standard). The
ON to OFF transition of circuit S nominally indicates the centre of each signal element on circuit
R in this case.
When Clock Polarity is set to "inverted", circuit T is sampled with the falling slope of S. The
incoming data at X.21 circuit T will be sampled at the OFF to ON transition of S.
3.4.9 Byte Timing
In the X.21 mode, the byte timing circuit B according to X.24 can be activated (configuration
option “BYTETIMING”). As the circuits B (byte timing) and X (co-directional transmit clock) share
the same pins on the 15-pin ISO 4903 connector, separate cables have to be used for these
cases.
3.4.10 Multiservice / nx64 Clock Modes
For V.35 and V.36, the receiving and the transmitting clock are independent. The receiving clock
is always the recovered remote clock. The clock mode configuration applies only to the transmit
clock. For X.21, there is only one clock (circuit S) to receive and transmit, the clock mode
determines the source of that single clock; however, in the co-directional nx64 Port clock mode,
X is used as a co-directional transmit clock and S is used only as receive clock. In the following
section the clock which can be selected by the clock mode is denoted as “transmit clock”.
The clock mode determines in most cases, whether the transmitting clock is co-directional (it
has the same direction as the transmit data, i.e. it is an input signal) or contra-directional (it has
the contrary direction of the transmitting data. i.e. it is an output signal).
Following clock modes are possible:
• nx64 Port: The transmitting clock is the co-directional clock coming from the equipment
connected to the nx64 port (circuit 113, X).
• E1 Port: The transmitting clock is generated by the transmit clock used at the E1 port. The
2048kHz E1 clock is fractionally synthesized to the bit rate configured and available at the
contra-directional transmit clock output (circuit 114). This clock mode should be used for
multiservice operation (simultaneous use of E1 and nx64 kbit/s).
• Internal: The transmitting clock is generated from the internal reference clock (contra-
directional, circuit 114).