The WAN Port Software Menu
Page 28-23
You can set up the external DCE this way by configuring its DTE, or dataport, configura-
tion options. Set the “Transmit Clock Source” to “External.” In this mode of operation, the
transmit clock is output by the DCE device and the submodule turns it around on the
external transmit clock back to the DCE, eliminating any phase misalignment between
transmit clock and transmit data.
If the external DCE does not provide a DTE configuration option for the transmit clock
source, then try setting the “Transmit Clock Polarity” to “Invert.” Note that Invert is the
clock polarity for Transmit (not Receive) and should only be used when excessive FCS
errors or Aborts are detected.
Internal Clocking
If you set this value to Internal, clocking is controlled by the internal DCE (the submod-
ule). Internal clocking should only be selected if the submodule is a physical DCE device
and you are using an RS-232 cable. Internal clocking is the default setting when the
submodule is a physical DCE device and an RS-232 DCE cable is connected to this port.
Split Clocking
Split clocking, which is also known as “loop timing,” uses an additional control signal
(TXCE) to keep the submodule and external DTE clocking synchronized. In split clocking,
the external DTE takes the incoming transmit clock from the submodule and loops it back
to TXCE. The submodule then uses this signal to clock in data from the external DTE
device. Split clocking should only be used if the submodule is a physical DCE device and
you are using a non-RS-232 cable, such as V.35.
♦ Important Note ♦
Split clocking is required if the access rate of the
submodule port is greater than 256 kbps and it is acting
as a DCE device. If split clocking is not used at these
data rates, data out-of-phase errors, aborts, or CRC
errors may occur.
Split clocking is the default when the submodule port is a physical DCE device and a non-
RS-232 DCE cable is connected to the port.
Protocol Type
The protocol type can be set to either Frame Relay or Point to Point Protocol (PPP). The
default setting is Frame Relay.
♦ Important Note ♦
A port must be set to either Frame Relay or PPP before
any other protocol-related parameters can be set.
TOS for Voice Data
Set the priority for voice data streams. The value must be entered in hexadecimal format
translated from binary, and can use either IP Precedence or Differentiated Services Code Point
(DSCP). Enter 0 to disable this feature. See Type of Service (ToS) on page 28-2 above for a
more detailed explanation of ToS.