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FALC56 V1.2
PEB 2256
Functional Description E1
Data Sheet
87
2002-08-27
4.2.3.7
S
a
-Bit Access (E1)
Due to signaling procedures using the five S
a
-bits (S
a4
…S
a8
) of every other frame of the
CRC multiframe structure, three possibilities of access by the microprocessor are
implemented.
The standard procedure allows reading/writing the S
a
-bit registers RSW, XSW without
further support. The S
a
-bit information is updated every other frame.
The advanced procedure, enabled by bit FMR1.ENSA, allows reading/writing the S
a
-
bit registers RSA4…8, XSA4…8.
A transmit or receive multiframe begin interrupt (ISR0.RMB or ISR1.XMB) is provided.
Registers RSA(8:4) contains the service word information of the previously received
CRC-multiframe or 8 doubleframes (bit slots 4 to 8 of every service word). These
registers are updated with every multiframe begin interrupt ISR0.RMB.
With the transmit multiframe begin an interrupt ISR1.XMB is generated and the contents
of the registers XSA(8:4) is copied into shadow registers. The contents is subsequently
sent out in the service words of the next outgoing CRC multiframe (or every
doubleframe) if none of the time slot 0 transparent modes is enabled. The transmit
multiframe begin interrupt XMB request that these registers issue should be serviced. If
requests for new information are ignored, the current contents is repeated.
The extended access through the receive and transmit FIFOs of the signaling
controller. In this mode it is possible to transmit/receive a HDLC frame or a transparent
bit stream in any combination of the S
a
-bits. Enabling is done by setting of bit
CCR1.EITS and the corresponding bits XC0.SA8E to SA4E/TSWM.TSA8 to TSA4
and resetting of registers TTR(4:1), RTR(4:1) and FMR1.ENSA. The access to and
from the FIFOs is supported by ISR0.RME, RPF and ISR1.XPR, ALS.
S
a
6-Bit Detection according to ETS 300233
Four consecutive received S
a
6-bits are checked for the combinations defined by
ETS
300233. The FALC56 detects the following fixed S
a
6-bit combinations: SA61,
SA62, SA63, SA64 = 1000, 1010, 1100, 1110, 1111. All other possible 4-bit
combinations are grouped to status “X”.
A valid S
a
6-bit combination must occur three times in a row. The corresponding status
bit in register RSA6S is set. Register RSA6S is of type “clear on read”. Any status change
of the S
a
6-bit combinations causes an interrupt (ISR0.SA6SC).
During the basic frame asynchronous state update of register RSA6S and interrupt
status ISR0.SA6SC is disabled. In multiframe format the detection of the S
a
6-bit
combinations can be done either synchronously or asynchronously to the submultiframe
(FMR3.SA6SY). In synchronous detection mode updating of register RSA6S is done in
the multiframe synchronous state (FRS0.LMFA = 0). In asynchronous detection mode
updating is independent of the multiframe synchronous state.