
QuadFALC
TM
PEF 22554 E
Functional Description E1
Data Sheet
142
Rev. 1.2, 2006-01-26
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.
Undisturbed operation starts with the beginning of the next doubleframe.
4.4.2.3
A-Bit Access (E1)
If the QuadFALC
TM detects a remote alarm indication in the received data stream the interrupt status bit ISR2.RA
is set. With setting of bit XSW.XRA a remote alarm (RAI) is sent to the far end.
By setting FMR2.AXRA the QuadFALC
TM 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 can be processed by the system interface. Setting bit TSWM.TRA enables transparency for the A-
bit in transmit direction (refer to Table 36).
4.4.2.4
S
a-Bit Access (E1)
As an extension for access to the S
a-bits through registers RSA(8:4) and XSA(8:4) an option is implemented to
allow the usage of internal S
a-bit registers RSA(8:4) and XSA(8:4) in doubleframe format.
This function is enabled by setting FMR1.ENSA = 1 for the transmitter and FMR1.RFS(1:0) = 01
B for the receiver.
In this case the QuadFALC
TM
internally works with a 16-frame structure but no CRC multiframe
alignment/generation is performed.
4.4.3
CRC-Multiframe (E1)
The multiframe structure shown in Table 38 is enabled by setting bit: FMR2.RFS(1:0) for the receiver and
FMR1.XFS for the transmitter.
Multiframe
:
2 submultiframes = 2 x 8 frames
Frame alignment
:
Refer to section Doubleframe Format
Multiframe alignment
:
Bit 1 of frames 1, 3, 5, 7, 9, 11 with the pattern 001011
B
CRC bits
:
Bit 1 of frames 0, 2, 4, 6, 8, 10, 12, 14
CRC block size
:
2048 bit (length of a submultiframe)
CRC procedure
:
CRC4, according to ITU-T G.704 and G.706