D. Pin AssignmentsD-6 February 2001 3160-A2-GB21-90COM Port InterfaceThe COM port connects to a PC for front panel emulation, to an ASCII terminal orprinter for alarms, to an async terminal, to a network device (e.g., a router) forSNMP or Telnet applications, to the LAN Adapter for SNMP or Telnet applications,or to another DSU/CSU’s AUX port for daisy chain connectivity. (The SNMP LANAdapter includes the cable that is needed to attach it to the DSU/CSU.) TheCOM port connector is an 8-position keyed modular connector (Table D-6, COMPort Connector). The data signals on this port are referenced to a DTE interface.The COM port-to-PC cable is shown in Figure D-5, COM Port-to-PC Cable, andthe COM port-to-terminal/printer cable is shown in Figure D-6, COMPort-to-Terminal/Printer Cable.NOTE:For daisy-chaining an AUX port to a COM port, a 25-pin-to-8-pin cable isrequired and the appropriate configuration options (Com Use and Aux Use)must be set to Daisy. Whenever the cable is connected or disconnected, youshould change the Daisy selection to ensure that the correct parameters havebeen negotiated for the link layer.Table D-6. COM Port ConnectorSignal Direction Pin NumberDCE Transmit Clock From DSU/CSU 1DCE Receive Data From DSU/CSU 2Signal Ground — 3DCE Transmit Data To DSU/CSU 4DCE Data Terminal Ready To DSU/CSU 5DCE Carrier Detect From DSU/CSU 6DCE Request-to-Send To DSU/CSU 7DCE Receive Clock From DSU/CSU 8
