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PEB 3445 E
Functional Description
Data Sheet
53
2001-06-29
4.6
Signalling Controller
The signalling controller provides access to the Far End Alarm and Control Channel and
to the C-bit Parity Path Maintenance Data Link Channel.
Note: The C-bit parity path maintenance data link channel and the far end alarm and
control channel support the same register structure. Registers assigned to the C-
bit parity path maintenance data link channel start with a ’P’, registers assigned to
the Far End Alarm and Control Channel start with a ’F’.
4.6.1
The TE3-MUX performs the FLAG generation, CRC generation, zero bit-stuffing and
programmable idle code generation. Buffering of transmit/receive data is done in 2x32
byte deep FIFOs.
The TE3-MUX additionally supports DMA support signals for operation of the C-bit parity
path maintenance data link channel.
C-bit Parity Path Maintenance Data Link Channel
Shared Flags
The closing flag of a previously transmitted frame simultaneously becomes the opening
flag of the following frame if there is one to be transmitted. The shared flag feature is
enabled by setting PXCR.SF.
CRC check
As an option in HDLC mode the internal handling of received and transmitted CRC
checksum can be influenced via control bits PRCFG.CRCDIS and PXCFG.DISCRC.
Receive Direction
The received CRC checksum is always assumed to be in the last two bytes of a frame,
immediately preceding a closing flag. If PRCFG.CRCDIS is set, the received CRC
checksum will be written to the receive FIFO where it precedes the frame status byte.
The received CRC checksum is additionally checked for correctness.
Transmit Direction
If PXCFG.DISCRC is set, the CRC checksum is not generated internally. The
checksum has to be provided via the transmit FIFO (PXFF.XFIFO) as the last two
bytes. The transmitted frame will only be closed automatically with a (closing) flag.
4.6.2
The BOM controller supports the Far End Alarm and Control Channel according to ANSI
T1.404.
Far End Alarm And Control Channel (BOM)