
PEB 2255
FALC-LH V1.3
Functional Description E1
Data Sheet
8
5
2000-07
The resynchronization procedure starts automatically after reaching the asynchronous
state. Additionally, it may be invoked user controlled via bit: FMR0.FRS (Force
Resynchronization: the FAS word detection is interrupted until the framer is in the
asynchronous state. After that, resynchronization starts automatically).
Synchronous state is established after detecting:
a correct FAS word in frame n,
the presence of the correct service word (bit 2
=
1) in frame n
+
1,
a correct FAS word in frame n
+
2.
If the service word in frame n
+
1 or the FAS word in frame n
+
2 or both are not found
searching for the next FAS word starts in frame n
+
2 just after the previous frame
alignment signal.
Reaching the synchronous state causes a frame alignment recovery interrupt status
ISR2.FAR if enabled.
U
ndisturbed operation starts with the beginning of the next
doubleframe.
4.4.2.3
If the FALC
-LH detects a remote alarm indication in the received data stream the
interrupt status bit ISR2.RA is set. With setting of bit
X
SW.
X
RA a remote alarm (RAI) is
send to the far end.
By setting FMR2.A
X
RA the FALC
-LH automatically transmit 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.
Note: The A-bit may be processed via the system interface. Setting bit TSWM.TRA
enables transparency for the A bit in transmit direction (refer to
Table Table 18
).
A-Bit Access
4.4.2.4
S
a
- Bit Access
As an extension for access to the S
a
-bits via registers RSA
4
-
8
/
X
SA
4
-
8
an option is
implemented to allow the usage of internal S
a
-bit registers RSA
4
-
8
/
X
SA
4
-
8
in
doubleframe format.
This function is enabled by setting FMR1.ENSA
=
1 for the transmitter and FMR1.RFS1/
0
=
01 for the receiver. The FALC
-LH works then internally with a 16-frame structure
but no CRC multiframe alignment/generation is performed.