W6691CD WINBOND [Winbond], W6691CD Datasheet - Page 38

• Manufacturer Part Number: W6691CD
• Description: ISDN S/T Interface Transceiver
• Manufacturer: WINBOND [Winbond]

7.2.7Multiframe Synchronization
auxiliary framing bit (F
positions and multiframe structure are shown in Table 7.10.
-
-
-
-
-
-
As specified by ITU-T I.430, the Q bit is transmitted from TE to NT in the position normally occupied by the
The functions provided by W6691 are:
Multiframe synchronization: Synchronization is achived when the M bit pattern has been correctly received
during 20 consecutive frames starting from frame number 1.
Note: Criterion for multiframe synchronization is not defined in I.430 Recommendation.
S bits receive and detect: When synchronization is achieved, the four received S bits in frames 1,6,11,16
are stored as S1 to S4 in the SQR register respectively. A change in the recived four bits (S1-4) is
indicated by an interrupt.
Multiframe synchronization monitoring: Multiframe synchronization is constantly monitored. The
synchronization state is indicated by the MSYN bit in the SQR register.
Q bits transmit and F
the SQXR register are transmitted as the four Q bits (F
the F
at the next F
The multiframe synchronization can be disabled by setting MFD bit in the D_MODE register.
According to I.430 Recommendation, the S/Q channel can be used as operation and maintenance
signalling channel. At transmitter, a S/Q code for a message shall be repeated at least six times or as
many as necessary to obtain the desired response. At receiver, a message shall be considered received
only when the proper codes is received three consecutive times.
A
bit transmitted is a mirror of the received F
A
-bit.
A
) in one frame out of 5, whereas the S bit is transmitted from NT to TE. The S and Q bit
A
mirroring: When multiframe synchronization is achived, the four bits Q1-4 stored in
A
-bit. At loss of synchronization, the mirroring is resumed
38
A
-bit position) in frames 1,6,11 and 16. Otherwise
Preliminary W6691
Publication Release Date: Sep 2001
Revision 1.1