Specifications

Configure a Synchronous Serial Interface
IC-78
Cisco IOS Interface Configuration Guide
To configure the interface so that the router inverts the TXC clock signal, use the following command
in interface configuration mode:
Specify G.703 and E1-G.703/G.704 Interface Options
This section describes the optional tasks for configuring a G.703 serial interface (a serial interface
that meets the G.703 electrical and mechanical specifications and operates at E1 data rates). G.703
interfaces are available on port adapters for the Fast Serial Interface Processor (FSIP) on a
Cisco 4000 series or Cisco 7500 series router.
The E1-G.703/G.704 serial port adapters (PA-4E1G-120 and PA-4E1G-75) are available on Cisco
7500 series routers, Cisco 7200 series routers, and Cisco 7000 series routers with the 7000 Series
Route Switch Processor (RSP7000) and 7000 Series Chassis Interface (RSP7000CI). These port
adapters provide up to four E1 synchronous serial interfaces, which are compatible with and
specified by G.703/G.704. The PA-4E1G-120 supports balanced operation and the PA-4E1G-75
supports unbalanced operation with 15-pin, D-shell (DB-15) receptacles on the port adapters. Both
port adapters operate in full-duplex mode at the E1 speed of 2.048-Mbps.
Configuration tasks are described in these sections:
• Enable Framed Mode
• Enable CRC4 Generation
• Use Time Slot 16 for Data
• Specify a Clock Source
Enable Framed Mode
G.703 interfaces have two modes of operation: framed and unframed. By default, G.703 serial
interfaces are configured for unframed mode. To enable framed mode, use the following command
in interface configuration mode:
To restore the default, use the no form of this command or set the starting time slot to 0.
Enable CRC4 Generation
By default, the G.703 CRC4, which is useful for checking data integrity while operating in framed
mode, is not generated. To enable generation of the G.703 CRC4, use the following command in
interface configuration mode:
Command Purpose
dte-invert-txc Specify timing configuration to invert TXC clock
signal.
Command Purpose
timeslot start-slot - stop-slot Enable framed mode.
Command Purpose
crc4 Enable CRC4 generation.