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Cisco 819 Series Integrated Services Routers Software Configuration Guide
OL-23590-02
Chapter 8 Configuring the Serial Interface
How to Configure Serial Interfaces
• Configuring Half-Duplex and Bisync for Synchronous Serial Port Adapters on Cisco 819 ISRs,
page 8-8 (Optional)
• Configuring Compression of HDLC Data, page 8-9 (Optional)
• Using the NRZI Line-Coding Format, page 8-9 (Optional)
• Enabling the Internal Clock, page 8-10 (Optional)
• Inverting the Transmit Clock Signal, page 8-10 (Optional)
• Setting Transmit Delay, page 8-11 (Optional)
• Configuring DTR Signal Pulsing, page 8-11 (Optional)
• Ignoring DCD and Monitoring DSR as Line Up/Down Indicator, page 8-11 (Optional)
• Specifying the Serial Network Interface Module Timing, page 8-12 (Optional)
See the “Configuration Examples” section on page 8-19 for examples of configuration tasks described
in this chapter.
Specifying a Synchronous Serial Interface
To specify a synchronous serial interface and enter interface configuration mode, use one of the
following commands in global configuration mode.
Specifying Synchronous Serial Encapsulation
By default, synchronous serial lines use the High-Level Data Link Control (HDLC) serial encapsulation
method, which provides the synchronous framing and error detection functions of HDLC without
windowing or retransmission. The synchronous serial interfaces support the following serial
encapsulation methods:
• HDLC
• Frame Relay
• PPP
• Synchronous Data Link Control (SDLC)
• SMDS
• Cisco Serial Tunnel (STUN)
• Cisco Bisync Serial Tunnel (BSTUN)
• X.25-based encapsulations
To define the encapsulation method, use the following command in interface configuration mode.
Command Purpose
Router(config)# interface serial 0
Enters interface configuration mode.
Command Purpose
Router(config-if)# encapsulation {hdlc | frame-relay
| ppp | sdlc-primary | sdlc-secondary | smds | stun
| x25 | bstun}
Configures synchronous serial encapsulation.