Terminal Timing - Vocality V200 User Manual

Vocality User Manual
User Manual for V200
Valid for V08_08.02 or V08_48.02
Table 5-6 Unit 1 Slot 1 Data menu, identical for Unit 1 and Unit 2

5.14.5 Terminal Timing

Particularly at higher data rates, it is important to ensure that the clock and data both
follow the same path in each of the two directions, to ensure that their phase
relationship is adequately maintained.
In the direction from DCE to DTE, it is usual to have the DCE generate the RXC clock
from a PLL and to drive out RXC and RXD together in phase. The receiving DTE samples
RXD on active transitions of RXC, and since both have followed the same path and
therefore been subject to the same delays, reliable data reception by the DTE is assured.
In the direction from DTE to DCE, it may still be desirable to have the data rate
governed by the DCE. In this case, set the DCE to operate in TTP (or TTD) mode.
In this mode, the DCE provides a clock on TXC which may be used by the DTE to clock
out data on TXD. The DTE should drive out a clock on TT which is synchronous to the
data which it presents on TXD, which may normally be accomplished by looping back
TXC to TT at the DTE end of the link. Since both clock and data are then subject to the
same delays from DTE to DCE, they arrive in phase and reliable reception by the DCE
port is also assured.
All Vocality DTE ports drive TT with the transmit data clock for this reason. It is expected
that a TT clock signal will be used, unless connected equipment is unable to support
this signal.
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