XRT74L73 Datasheet, PDF (252/488 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 91. FLOW DIAGRAM DEPICTING HOW THE RECEIVE FEAC PROCESSOR FUNCTIONS
SSTTAARRTT
11
EENNAABBLLEETTHHEE““FFEEAACCRREEMMOOVVAALLAANNDD
““VVAALLIDIDAATTIOIONN””ININTTEERRRRUUPPTTSS. _.
TThhisisisisacaccocommpplilsihshededbbyywwrirtiitningg“x“xxxxxxx11001100””inintotoththee
“R“RxDxDSS33FFEEAACCInItnetrerrurputp/tS/StattautsusRRegeigsitsetrer(A(Adddrdersesss==0x01x71)7)
RREECCEEIVIVEEFFEEAACCPPRROOCCEESSSSOORRBBEEGGININSSRREEAADDININGGININ
TTHHEEFFEEAACCBBITIT-F-FIEIELLDDSS(O(OFFININCCOOMMININGGDDSS33FFRRAAMMEESS) ₎
TTheheRReceecievieveFFEEAACCPProrcoecsessosor _{rchchecekcks sfofrorthtehe“F“FEEAACCFFrarmaminigng}
AAlilgingmnmenent”t”ppatattetrenrnoof _{f“0“10111111111101”0.”.}
IsIsthtehe
“F“FEEAACCFFrarmaminigng
AAlilgignmnmenent”tp”aptattetrenrn
NO
prperseesnetntininthteheFFEEAACC _NO
CChhanannenlel
??
YES
RREEAADDININTTHHEE““66-B-BITITFFEEAACCCCOODDEEWWOORRDD””
TThhee66-b-bititFFEEAACCCCooddeeWWoordrdimimmmedeidaitaetleylyfoflollolwows _{sthtehe“F“FEEAACC}
FFrarmaminigngAAlilgingmnmenetn”t”PPatattetrenrn. _.
HHasasthtihsis
sasmameeFFEEAACC
CCodoedeWWorodrdbebeenen
YES
RReceecievievdedinin88oouut _{toof fththeelalsatst}
1010FFEEAACCMMesessasgagee
RReceecpetpitoionns?s?
NO
GGEENNEERRAATTEE““FFEEAACC
VVAALLIDIDAATTIOIONN””ININTTEERRRRUUPPTT
ININVVOOKKEE““FFEEAACCVVAALLIDIDAATTIOIONN””
ININTTEERRRRUUPPTTSSEERRVVICICEERROOUUTTININEE. _.
HHasasaaFFEEAACC
CCooddeeWWoordrd(o(othtehrerthtahnan
ththeelalsatst“V“ValaildidataetdedCCooddeeWWoordrd) ₎
bebeenenRReceecievievdedinin33oouut _{toof fththeelalsatst}
1010FFEEAACCMMesessasgagee
RReceecpetpitoinosn?s?
11
YES
GGEENNEERRAATTEE““FFEEAACC
RREEMMOOVVAALL””ININTTEERRRRUUPPTT
11
ININVVOOKKEE“F“FEEAACCRREEMMOOVVAALL””
ININTTEERRRRUUPPTTSSEERRVVICICEERROOUUTTININEE. _.
NOTES:
1. The white (e.g., unshaded) boxes reflect tasks that
the user’s system must perform in order to config-
ure the Receive FEAC Processor to receive FEAC
messages.
2. A brief description of the steps that must exist
within the FEAC Validation and FEAC Removal
Interrupt Service Routines exists in Section 4.3.3
4.3.3.2 The Message Oriented Signaling (e.g.,
LAP-D) Processing via the Receive DS3 HDLC
Controller block
The LAPD Receiver (within the Receive DS3 HDLC
Controller block) allows the user to receive PMDL
messages from the remote terminal equipment, via
the inbound DS3 frames. In this case, the inbound
message bits will be carried by the 3 DL bit-fields of
F-Frame 5, within each DS3 M-Frame. The remote
LAPD Transmitter will transmit a LAPD Message to
the Near-End Receiver via these three bits within
each DS3 Frame. The LAPD Receiver will receive
and store the information portion of the received
LAPD frame into the Receive LAPD Message Buffer,
which is located at addresses: 0xDE through 0x135
within the on-chip RAM. The LAPD Receiver has the
following responsibilities.
• Framing to the incoming LAPD Messages
• Filtering out stuffed 0s (within the information pay-
load)
• Storing the Frame Message into the Receive LAPD
Message Buffer
• Perform Frame Check Sequence (FCS) Verification
• Provide status indicators for
End of Message (EOM)
Flag Sequence Byte detected
Abort Sequence detected
Message Type
C/R Type
The occurrence of FCS Errors
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