PM6341 E1XC
DATA SHEET
PMC-910419
ISSUE 8
E1 FRAMER/TRANSCEIVER
of CRC multiframe, based on user-selectable criteria. The reframe operation can
be initiated by software (via the FRMR Frame Alignment Options Register), by
excessive CRC errors, or when CRC multiframe alignment is not found within 8
ms. The FRMR also identifies the position of the frame, the CAS multiframe, and
the CRC multiframe.
The FRMR extracts timeslot 16 for optional use as a data link and also extracts
the contents of the International bits (from both the FAS frames and the NFAS
frames), the National bits, and the Extra bits (from timeslot 16 of frame 0 of the
CAS multiframe), and stores them in the FRMR International/National Bits
Register, and the FRMR Extra Bits Register respectively.
The FRMR identifies the raw bit values for the remote (or distant frame) alarm
(bit 3 in timeslot 0 of NFAS frames) and the remote signalling multiframe (or
distant multiframe) alarm (bit 6 of timeslot 16 of frame 0 of the CAS multiframe)
via the FRMR International/National Bits Register, and the FRMR Extra Bits
Register respectively. Access is also provided to the "debounced" remote alarm
and remote signalling multiframe alarm bits which are set when the
corresponding signals have been a logic 1 for 2 or 3 consecutive occurrences, as
per Recommendation O.162. Detection of AIS and timeslot 16 AIS are provided;
AIS is also integrated and an AIS Alarm is indicated if the AIS condition has
persisted for at least 100 ms. The out of frame (OOF=1) condition is also
integrated, indicating a red Alarm if the OOF condition has persisted for at least
100 ms.
An interrupt may be generated to signal a change in the state of any status bits
(OOF, OOSMF, OOCMF, AIS, or RED), and to signal when any event (RRA,
RRMA, AISD, T16AISD, COFA, FER, SMFER, CMFER, CRCE, or FEBE) has
occurred.
9.4.1 Frame Find
The Frame Find Block searches for frame alignment using one of two user-
selectable algorithms, as defined in Recommendation G.706. Optionally, a two
frame check sequence can be added to either algorithm to provide protection
against false frame alignment in the presence of random mimic patterns.
The first algorithm finds frame alignment by using the following sequence:
1. Search for the presence of the correct 7-bit FAS;
2. Check that the FAS is absent in the following frame by verifying that bit 2 of the
assumed timeslot 0 byte is a logic 1;
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
44
PMC [ PMC-SIERRA, INC ]
