XRT79L71
PRELIMINARY
147
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
1.
It permits a Terminal which is transmitting a DS3 data stream to a remote terminal to determine whether
or not this remote terminal is receiving its DS3 data, in an error-free manner.
2.
It permits a Terminal which is receiving a DS3 data stream from a remote terminal to inform this remote
terminal when it is receiving erred DS3 frames.
The role of the FEBE bit-field is best presented in the practical example below.
Example:
Consider a Near-End terminal that is communicating with a remote terminal. This Near-End terminal consists
of the Transmit DS3/E3 Framer block and the Receive DS3/E3 Framer block within the XRT79L71 IC as
The Transmit DS3/E3 Framer block will generate and transmit DS3 frames to the remote terminal. Likewise,
the Receive DS3/E3 Framer block will receive and process DS3 frames, originating from the remote terminal.
The Near-End Receive DS3/E3 Framer block (e.g., the Receive DS3/E3 Framer block within this particular
device) is going to verify the values of the framing (e g., the F and M) bits, as well as the CP bits, within the
incoming DS3 frames from the remote terminal. If the Near-End Receive DS3/E3 Framer block detects no
framing bit or CP bit errors, in the incoming DS3 frame, then it will notify the remote terminal of this fact, by
forcing the Near-End Transmit DS3/E3 Framer block, set the FEBE bits within the very next outbound DS3
frame which is destined for the remote terminal to a 1, 1, 1 pattern.
This phenomenon is illustrated in
Figure 63 illustrates the Near-End Receive DS3/E3 Framer block receiving an error-free DS3 frame. In this
figure, the locally computed CP bits of "0" matches that received from the remote terminal.
illustrates the subsequent action of the Near-End Transmit DS3/E3 Framer block which will transmit a DS3
frame, with the FEBE bit-fields set to "1, 1, 1" to the remote terminal. This signaling indicates that the Near-
End Receive DS3/E3 Framer block has received an error-free DS3 frame from the remote terminal.
FIGURE 63. ILLUSTRATION OF THE NEAR-END RECEIVE DS3/E3 FRAMER BLOCK RECEIVING A DS3 FRAME FROM
THE REMOTE TERMINAL WITH CORRECT
F, M AND CP BITS
Transmit DS3
Framer
Receive DS3
Framer
Near-End Terminal
Remote
Terminal
Equipment
Remote
Terminal
Equipment