PEF2256EV22NP Lantiq, PEF2256EV22NP Datasheet - Page 97

• Manufacturer Part Number: PEF2256EV22NP
• Manufacturer: Lantiq

Specifications of PEF2256EV22NP

• Number Of Transceivers: 1
• Screening Level: Industrial
• Mounting: Surface Mount
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Lead Free Status / RoHS Status: Supplier Unconfirmed

®
FALC
56
PEF 2256 H/E
Functional Description E1
frame alignment) is established, a 400-ms timer and searching for multiframe alignment
are started. A research for basic frame alignment is initiated if the CRC4 multiframe
synchronization cannot be achieved within 8 ms and is started just after the previous
frame alignment signal. The research of the basic frame alignment is done in parallel and
is independent of the synchronization procedure of the primary basic frame alignment
signal. During the parallel search all receiver functions are based on the primary frame
alignment signal, like framing errors, S
-, S
-, A-bits, …). All subsequent multiframe
a
i
searches are associated with each basic framing sequence found during the parallel
search.
If the CRC4 multiframe alignment sequence was not found within the time interval of
400 ms, the receiver is switched into a non-CRC4 mode indicated by setting the bit
FRS0.NMF (No Multiframing Found) and ISR2.T400MS. In this mode checking of CRC
bits is disabled and the received E-bits are forced to low. The transmitter framing format
is not changed. Even if multiple basic FAS resynchronizations have been established
during the parallel search, the receiver is maintained to the initially determined primary
frame alignment signal location.
However, if the CRC4-multiframe alignment can be achieved within the 400 ms time
interval assuming a CRC4-to-CRC4 interworking, then the basic frame alignment
sequence associated to the CRC4 multiframe alignment signal is chosen. If necessary,
the primary frame alignment signal location is adjusted according to the multiframe
alignment signal. The CRC4 performance monitoring is started if enabled by
FMR2.ALMF and the received E-bits are processed in accordance to ITU-T G.704.
Switching into the doubleframe format (non-CRC4) mode after 400 ms can be disabled
®
by setting of FMR3.EXTIW. In this mode the FALC
56 continues to search for
multiframing. In the interworking mode setting of bit FMR1.AFR is not allowed.
6.2.3.6
A-Bit Access (E1)
®
If the FALC
56 detects a remote alarm indication (bit 2 in TS0 not containing the FAS
word) in the received data stream the interrupt status bit ISR2.RA is set. With the
deactivation of the remote alarm the interrupt status bit ISR2.RAR is generated.
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By setting FMR2.AXRA the FALC
56 automatically transmits the remote alarm bit = 1 in
the outgoing data stream if the receiver detects a loss of frame alignment
(FRS0.LFA = 1). If the receiver is in synchronous state (FRS0.LFA = 0), the remote
alarm bit is reset in the outgoing data stream.
Additionally, if bit FMR3.EXTIW is set and the multiframe synchronous state cannot be
achieved within 400 ms after finding the primary basic framing, the A-bit is transmitted
active high to the remote end until the multiframing is found.
Note: The A-bit can be processed by the system interface. Setting bit TSWM.TRA
enables transparency for the A-bit in transmit direction (refer to
Table
21).
Data Sheet
97
Rev. 1.1, 2005-06-13