Perle Systems 1700 - Manual (Page 89)

Servicing Information
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Appendix D
Interface Pinouts
Pinout Information
Each link interface available is described with detailed information on pin designation. Standard interface
cables will provide correct connections to modems, datasets, or DSU/CSUs.
When connecting two bridge/routers back-to-back without modems, a null-modem cable is
required to crossover the pins on the links. Crossing over the pins allows two bridge/routers
both configured as DTE interfaces to be connected together. With this configuration, both
bridge/routers will provide clocking for the links, and each bridge/router must have a link speed
defined.
Link Clocking Information
All of the link interfaces on the router act as DTE devices, this means that they may be directly
connected to DCE devices (modems, etc.) with the DCE devices providing the clocking for the
link. The link speed is controlled by the DCE device. Setting the link speed on the router will
not result in a speed change on the link.
Some DCE devices allow the DTE devices connected to them to supply a clock signal which is
then routed back to the transmit clock pins on the DCE interface. This clock is then received by
the router link interface. By using this method, the router may be in control of the link speed.
The link speed may also be controlled by the router when a null-modem cable is used to
connect two routers in a back-to-back configuration.
Changing the link speed within the menu system of the router changes the clock output speed
that is generated on the DTE Terminal Timing pins (external clocking pins) on the link
interfaces.
ATL-CSU/DSU Link Module Information
The P1705 & P1730 are currently produced with LXT CSU/DSU interface modules; however,
the earlier model ATL CSU/DSU module is still compatible with the router and may be used
with it. Note that ATL master mode signaling is not compatible with the current standard 64K
master mode signaling; therefore, for back to back connections, an ATL unit will only operate at
64K when connected to another ATL unit. If one interface is an ATL unit and the other is not,
back to back operation must be set to 56K.
The ATL-CSU/DSU link module is normally configured to receive clock from the connected
network. When two ATL-CSU/DSU link modules are to be used on a leased line in a back-to-
back set-up, one of the modules must provide the clock.