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PRELIMINARY
DS3 UNI FOR ATM
XRT7245
REV. 1.03
239
Bit 1—RxLAPD Interrupt Enable
This bit-field allows the user to enable/disable the
“RxLAPD Interrupt”. Writing a “1” to this bit-field
enables this interrupt. Whereas, writing a “0” disables
this interrupt. The value of this bit-field is “0” following
power up or reset.
7.2
Receive PLCP Processor
7.2.1
The Receive PLCP Processor receives PLCP frame
data from the Receive DS3 Framer and locates the
boundaries of these incoming PLCP frames. The
Receive PLCP processor also extracts the PLCP
overhead bytes, computes and verifies the incoming
BIP-8 (B1) byte, transfers FEBE and Yellow Alarm
information to the “Near-End” Transmit PLCP
Processor, for transmittal back to the Far-End Terminal.
Finally, these PLCP frames (and their designated
boundaries) are routed to the Receive Cell Processor,
for further processing.
Operation of the Receive PLCP Processor
Note:
The Receive PLCP Processor is disabled when the
UNI is operating in the “Direct Mapped ATM” mode.
Figure 72 presents a simple illustration of the Receive
PLCP Processor block along with the associated
external pins.
7.2.2
Functional Description of the Receive
PLCP Processor
The Receive PLCP Processor receives and operates
on data extracted from the payload-portion of the
incoming DS3 data stream (via the Receive DS3
Framer). Once the Receive DS3 Framer reaches the
“In-Frame” state, then the Receive PLCP Processor
will take this incoming data and begin searching for
the PLCP frame boundaries. The Receive PLCP
Processor will inform the “outside world” that it has
began detecting these PLCP frame boundaries by
pulsing the RxPFrame output pin. Figure 73, presents
a Functional Block Diagram of the Receive PLCP
Processor and Table 51 presents the Byte Format for
a PLCP Frame.
F
IGURE
72. I
LLUSTRATION
OF
THE
S
IMPLE
B
LOCK
D
IAGRAM
OF
THE
R
ECEIVE
PLCP P
ROCESSOR
To Rx Framer
To Rx Cell Processor
RxPOHClk
RxPOHFrame
RxPOH
RxPFrame
RxPLOF
RxPOOF
Receive PLCP
Processor