
FALC56 V1.2
PEB 2256
Functional Description E1
Data Sheet
81
2002-08-27
Table 17
4.2.2.2
Synchronization Procedure
Synchronization status is reported by bit FRS0.LFA. Framing errors are counted by the
Framing Error Counter (FEC). Asynchronous state is reached after detecting 3 or 4
consecutive incorrect FAS words or 3 or 4 consecutive incorrect service words (bit 2 = 0
in time slot 0 of every other frame not containing the frame alignment word), the selection
is done by bit RC0.ASY4. Additionally, the service word condition can be disabled. When
the framer lost its synchronization an interrupt status bit ISR2.LFA is generated.
In asynchronous state, counting of framing errors and detection of remote alarm is
stopped. AIS is automatically sent to the backplane interface (can be disabled by bit
FMR2.DAIS).
Further on the updating of the registers RSW, RSP, RSA(8:4), RSA6S and RS(16:1) is
halted (remote alarm indication, S
a
/S
i
-Bit access).
The resynchronization procedure starts automatically after reaching the asynchronous
state. Additionally, it can be invoked user controlled by 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.
Transmit Transparent Mode (Doubleframe E1)
Transmit Transparent Source for
Framing
A-Bit
(int. gen.)
via pin XDI
1)
(int. gen.)
(int. gen.)
(int. gen.)
(int. gen.)
XSW.XRA
Enabled by
–
XSP.TT0
TSWM.TSIF
TSWM.TSIS
TSWM.TRA
TSWM.TSA(8:4)
S
a
-Bits
XSW.XY0…4
3)
S
i
-Bits
XSW.XSIS, XSP.XSIF
via pin XDI
via pin XDI
via pin XDI
XSW.XSIS, XSP.XSIF
XSW.XSIS, XSP.XSIF
1)
pin XDI or XSIG or XFIFO buffer (signaling controller)
XSW.XRA
2)
via pin XDI
XSW.XRA
XSW.XRA
via pin XDI
2)
Additionally, automatic transmission of the A-bit is selectable.
via pin XDI
XSW.XY0…4
XSW.XY0…4
XSW.XY0…4
via pin XDI
3)
As a special extension for double frame format, the S
a
-bit register can be used optionally.