XRT74L73 Datasheet, PDF (458/488 Pages) Exar Corporation – 3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER

XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
PRELIMINARY
FIGURE 208. FLOW CHART DEPICTING THE FUNCTIONALITY OF THE LAPD RECEIVER
START
Indicate whether the LAPD Receiver should retrieve the
LAPD Message frame octets from the NR or GC byte-field,
within each incoming E3 Frame.
Enable the LAPD Receiver
The LAPD Receiver will begin searching for the Flag Sequence
octet (0x7E) in the “selected” byte-field (e.g., NR or GC) of each
incoming E3 frame.
Is
Flag Sequence
No
octet
Present?
Yes
Assert the “Flag Present” bit-field within the “Rx E3 LAPD
Status Register (Address = 0x19).
Is
non-Flag Sequence ^Yes
octet detected
?
No
Set the “RxLAPDType[1:0] bit-fields to the appropriate value.
Continue to read in the LAPD Message frame octets
Is
Abort Sequence
Yes
Detected?
No
A
Has
the last byte
No _{of the LAPD Message}
frame been
received?
Yes
Set the “End Of Message” bit-field within the “RxE3
LAPD Status Register (Address = 0x19)
Unstuff the “PMDL” portion of the LAPD Message frame.
Goto Figure 185
459