Data Synchronization - Paradyne COMSPHERE 3920PLUS Technical Reference Manual

COMSPHERE 392xPlus Modems

Data Synchronization

Data exchanged between the synchronous DTE and the modem is synchronized by two clock
signals. Data coming from the DTE is synchronized by the transmit clock and data received by the
DTE is synchronized by the receive clock. The transmit clock is provided by the modem on circuit
114 or by the synchronous DTE on circuit 113. The receive clock is provided by the modem on
circuit 115.
When the transmit clock is provided by the modem, the transmit and receive clocks are locked on
the same clock source internal to the modem. In this configuration, you can select rates on the
DTE-DCE line (or clock frequencies) in the range from 1.2 kHz to 128 kHz.
When the transmit clock is provided by the DTE, the receive clock is set by the modem equal to
the DTE clock (Figure H-4). When SDC is in use, the Tx Clock Source configuration option
cannot be set to Receiver Clock Loop.
DTE
H-4
When faster speeds are used (above 57.6 kHz), and the transmit
clock is provided by the modem, data transmission can be sensitive
to DTE cable length and capacitance, as well as the DTE's drivers
and receivers. Should you encounter bit errors related to the above
conditions, you may want to change the Tx Clock Source
configuration option setting to External (provided the DTE can
support the required transmit clock signal) or change the length of
the DTE cable.
XTCLK (113)
Figure H-4. Clocks at the DTE–DCE Interface
October 1998
NOTE
DCE
TXC (114)
RXC (115)
CLOCK
SOURCE
495-14782
3920-A2-GH30-40