
PEB 2255
FALC-LH V1.3
Functional Description T1/J1
Data Sheet
1
44
2000-07
5.4.5.2
Remote Alarm (yellow alarm) Generation/Detection
Remote alarm (yellow alarm) is indicated by the periodical pattern ‘1111 1111 0000 0000
…’ in the DL bits. Remote alarm is declared even in the presence of BER 1/1000. The
alarm is reset when the “yellow alarm pattern“ no longer is detected.
Depending on bit RC1.SJR the FALC
-LH generates and detect the Remote Alarm
according to JT G. 70
4
. In the DL-bit position 16 continuos “1“ are transmitted if
FMR0.SRAF
=
0 and FMR
4
.
X
RA
=
1.
Alternatively remote alarm can be indicated by setting bit 2 of every time slot after
selecting FMR0.SRAF
=
1.
5.4.5.3
CRC6 Generation and Checking (T1/J1)
Generation and checking of CRC6 bits transmitted/received in the e1-e6 bit positions is
done according to IT
U
-T G.706. The CRC6 checking algorithm is enabled via bit
FMR1.CRC. If not enabled, all check bits in the transmit direction are set. In the
synchronous state received CRC6 errors are accumulated in a 16 bit error counter and
are additionally indicated by an interrupt status.
CRC6 Inversion
If enabled by bit RC0.CRCI, all CRC bits of one outgoing extended multiframe are
automatically inverted in case a CRC error is flagged for the previous received
multiframe. Setting the bit RC0.
X
CRCI inverts the CRC bits before transmitted to the
distant end. This function is logically ored with RC0.CRCI.
CRC6 Generation/Checking According to JT G. 706
Setting of RC1.SJR the FALC
-LH generates and check the CRC6 bits according to
JT G. 706. The CRC6 checksum is calculated including the FS/DL bits. In synchronous
state CRC6 errors increment an error counter.
5.4.6
72-Frame Multiframe (SLC96 Format, T1/J1)
The 72-multiframe is an alternate use of the FS-bit pattern and is used for carrying data
link information. This is done by stealing some of redundant multiframing bits after the
transmission of the 12-bit framing header (refer to
Figure 36
on page
146
). The position
of A and B signaling channels (robbed bit signaling) is defined by zero-to-one and one-
to-zero transitions of the FS bits and is continued when the FS bits are replaced by the
data link bits.
Remote Alarm (
Y
ellow Alarm) is indicated by setting bit 2 to zero in each time slot. An
additional use of the D bits for alarm indication is user defined and must be done
externally.