Datasheet

Installing 2T16S Network Processor Modules in the Cisco 4000 Series
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Installing 2T16S Network Processor Modules in the Cisco 4000 Series
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Note The configure command requires privileged-level access to the EXEC command interpreter, which
usually requires a password. Contact your system administrator to obtain access if necessary.
The following sections describe the commands for configuring an external clock signal for a DCE
interface and for configuring a port for NRZI encoding or 16-bit cyclic redundancy check (CRC).
Configuration commands are entered at the privileged level of the EXEC command interpreter.
Configuring Timing (Clock) Signals for Serial Interfaces
All serial interfaces support both DTE and DCE modes, depending on the mode of the interface cable
attached to the port. To use a port as a DTE interface, connect a DTE adapter cable to the port. When the
system detects the DTE mode cable, it automatically uses the external timing signal. To use a port in
DCE mode, you must connect a DCE interface cable and set the clock speed with the clockrate
configuration command. This section describes how to set the clock rate on a DCE port and, if necessary,
how to invert the clock to correct a phase shift between the data and clock signals.
Setting the Clock Rate on Serial Interfaces
All DCE interfaces require a noninverted internal transmit clock signal, which is generated by the serial
module. The default operation on a DCE interface is for the DCE device to generate its own clock signal
(TXC) and send it to the remote DTE. The remote DTE device returns the clock signal to the DCE. The
clockrate command specifies the rate as a bits-per-second value. In the following example, the clock
rate for the second high-speed serial interface on a 2T16S network processor module is defined as 2
Mbps:
interface serial 1
clockrate 2000000
Use the no clockrate command to remove the clock rate for DTE operation. Following are the acceptable
clock rate settings:
Speeds above 64 kbps (64000) are not supported for EIA/TIA-232. On all interface types, if your cable
is too long, faster speeds might not work.
Inverting the Clock Signal on Serial Interfaces
Systems that use long cables may experience high error rates when operating at the higher transmission
speeds. Slight variances in cable construction, temperature, and other factors can cause the clock and
data signals to shift out of phase. If a DCE port is reporting a high number of error packets, a phase shift
might have occurred. Inverting the clock can often correct this shift.
1200
2400
4800
9600
19200
38400
56000
64000
72000
125000
148000
500000
800000
1000000
1300000
2000000