
FALC56 V1.2
PEB 2256
Functional Description T1/J1
Data Sheet
161
2002-08-27
HDLC framing is performed. Optionally the FALC56 supports the continuous
transmission of the XFIFO contents.
Operating in HDLC or BOM mode
“
flags
”
or
“
idle
”
are transmitted as interframe timefill.
The FALC56 offers the flexibility to insert data during certain time slots. Any
combinations of time slots can be programmed separately for the receive and transmit
direction if using HDLC channel 1. HDLC channel 2 and 3 support one programmable
time slot common for receive and transmit direction each.
5.4.7.2
Support of Signaling System #7
The HDLC controller of channel 1 supports the signaling system #7 (SS7) which is
described in ITU-Q.703. The following description assumes, that the reader is familiar
with the SS7 protocol definition.
SS7 support must be activated by setting the MODE register. Data stored in the transmit
FIFO (XFIFO) is sent automatically. The SS7 protocol is supported by the following
hardware features in transmit direction:
transmission of flags at the beginning of each Signaling Unit
bit stuffing (zero insertion)
calculation of the CRC16 checksum:
The transmitter adds the checksum to each Signaling Unit.
Each signaling unit written to the transmit FIFO (XFIFO, 2
×
32 bytes) is sent once or
repeatedly including flags, CRC checksum and stuffed bits. After e.g. an MSU has
been transmitted completely, the FALC56 optionally starts sending of FISUs
containing the forward sequence number (FSN) and the backward sequence number
(BSN) of the previously transmitted signaling unit. Setting bit CCR5.AFX causes Fill
In Signaling Units (FISUs) to be sent continuously, if no HDLC or Signaling Unit (SU)
is to be transmitted from XFIFO. During update of XFIFO, automatic transmission is
interrupted and resumed after update is completed. The internally generated FISUs
contain FSN and BSN of the last transmitted signaling unit written to XFIFO.
Using CMDR.XREP = 1, the contents of XFIFO can be sent continuously. Clearing of
CMDR.XRES/SRES stops the automatic repetition of transmission. This function is
also available for HDLC frames, so no flag generation, CRC byte generation and bit
stuffing is necessary.
Example: After an MSU has been sent repetitively and XREP has been cleared,
FISUs are sent automatically.
5.4.7.3
CAS Bit-Robbing (T1/J1, serial mode)
The signaling controller inserts the bit stream either on the transmit line side or if external
signaling is enabled on the transmit system side. Signaling data is sourced on port XSIG,
which is selected by register PC(4:1) and FMR5.EIBR = 1.