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Data Sheet
135
Rev. 1.2, 2006-01-26
QuadFALC
TM
PEF 22554 E
Functional Description E1
interpreted as command/response bit (C/R) and is excluded from the address comparison. Buffering of receive
data is done in a 128 byte deep RFIFO. In signaling controller transparent mode, fully transparent data reception
without HDLC framing is performed, i.e. without flag recognition, CRC checking or bit stuffing. This allows user
specific protocol variations.
The transmit signaling controller of the QuadFALC
TM performs the flag generation, CRC generation, zero-bit
stuffing and programmable idle code generation. Buffering of transmit data is done in the 128 byte deep XFIFO.
The signaling information is internally multiplexed with the data applied to port XDI or XSIG. In signaling controller
transparent mode, fully transparent data transmission without HDLC framing is performed. Optionally the
QuadFALC
TM supports the continuous transmission of the XFIFO contents. The QuadFALCTM 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.
4.3.2
Support of Signaling System #7 (E1)
HDLC controller 1 of each of the four channels of the QuadFALC
TM 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 configuring the register bits MODE.MDS(3:0), see MODE_E. The SS7 protocol
is supported by the following hardware features in receive mode:
All Signaling Units (SU) are stored in the receive FIFO (RFIFO)
Detecting of flags from the incoming data stream
Bit stuffing (zero deletion)
Checking of seven or more consecutive ones in the receive data stream
Checking if the received Signaling Unit is a multiple of eight bits and at least six octets including the opening
flag
Calculation of the CRC16 checksum: In receive direction the calculated checksum is compared to the received
one; errors are reported in register RSIS.
Checking if the signal information field of a received signaling unit consists of more than 272 octets, in this case
the current signaling unit is discarded.
In order to reduce the microprocessor load, fill In signaling units (FISUs) are processed automatically. By
examining the length indicator of a received signal unit the QuadFALC
TM decides whether a FISU has been
received. Consecutively received FISUs are compared and optionally not stored in the receive FIFO (RFIFO), if
the contents is equal to the previous one. The same applies to link status signaling units, if bit CCR5.CSF
(CCR5_E) is set. The different types of signaling units as message signaling unit (MSU), link status signaling unit
(LSSU) and fill in signaling units (FISU) are indicated in the RSIS register, which is automatically added to the
RFIFO with each received signaling unit. The complete signaling unit except start and end flags is stored in the
receive FIFO. The functions of bits CCR2.RCRC and CCR2.RADD are still valid in SS7 mode (GPC2_E). Errored
signaling units are handled automatically according to ITU-T Q.703 as shown in Figure 45. SU counter (su) and
errored SU counter (C
s) are reset by setting CMDR2.RSUC. The error threshold T can be selected to be 64
(default) or 32 by setting/clearing bit CCR5.SUET (CCR5_E). If the defined error limit is exceeded, an interrupt
(ISR1.SUEX) is generated, if not masked by IMR1.SUEX = 1 (IMR0_E).
Note: If SUEX is caused by an aborted/invalid frame, the interrupt will be issued regularly until a valid frame is
received (e.g. a FISU).