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TTF BLOCK (SPI, RST, MST, MSA)
This block performs the Transport Terminal Functions (sink on Rx side, source on Tx side) for the STM–4
signal.
TTF block provides the T1 timing references at 2 MHz, derived from the STM–4 input signals.
INPUT side : from line to MSP MATRIX
SPI (OSn/RSn_A_Sk) : it descramblers the incoming signal, counts the OOF and reveals the LOF
alarm.
RST (RSn_TT_Sk) : performs frame alignment detection (A1, A2), regenerator section trace
recovery (J0) and mismatch detection, BIP–8 Errored Block count.
MST (MSn_TT_Sk) : performs BIP–24 errored block count, MS–REI recovery, MS–RDI and MS–AIS
detection. TSD is applied in case of MS–DEG (signal degrade), TSF is applied if MS–AIS is detected.
MSA (MSn/Sn_A_Sk) : performs AU4's pointer interpretation, LOP and AIS detection, pointer
justification.
Moreover the following functions are performed on the Rx side:
SOH BYTE extraction (Rx side) : DCC bytes (DCCR D1 B D3 and DCCM D4 B D12) are dropped
and serialized in a DCC frame. Two DCC frames are generated working in 1+1 protection.
TP byte insertion (Rx side) : since the cross connection functions are centralized, for protection
purpose TSD (Trail Signal Degrade) and TSF (Trail Signal Failure) are transmitted towards the two
HCMATRIX boards.
K BYTES insertion and extraction (Rx side) : this block provides the in–band transmission of K1,
K2, bytes towards the MATRIXE board. For each of the 4 STM–1 streams, the bytes are extracted
form the line when a TSF is received and they are overwritten into the SOH section.
OUTPUT side : from MATRIX to line
MSA (Ms/Sn_A_So) : it performs AUG assembly, AU–4 pointer generation, AU–AIS generation.
The four AUG structure are byte interleaved in the STM–4 structure with fixed phase relationship vs.
the same multiple signal.
MST (MSn_TT_So) : it performs BIP–24 calculation and insertion, MS–REI MS–RDI and MS–AIS
insertion.
RST (RSn_TT_So) : it performs frame alignment insertion, regenerator section path trace insertion,
BIP–8 calculation and insertion.
SOH BYTE insertion (Tx side) : DCC bytes (DCCR D1 B D3 and DCCM D4 B D12) coming
from the DCC frames are inserted into the SOH section.
K BYTES insertion and extraction (Tx side) : K1, K2 bytes are extracted from the frame coming
from backpanel and re–inserted on the same output line frame.
ED
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