TUSB1310A
SLLSE32D–NOVEMBER 2010–REVISED MAY 2011
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3.4.3 8b/10b Decode Errors
When the TUSB1310A detects an 8b/10b decode error, it will assert a SUB symbol in the data on the
RX_DATA where the bad byte occurred. In the same clock cycle that the SUB symbol is asserted on the
RX_DATA, the 8b/10b decode error code (100b) will be asserted on the RX_STATUS. 8b/10b Decoding
error has priority over all other receiver error codes and could mask out a disparity error occurring on the
other byte of data being clocked onto the RX_DATA with the SUB symbol.
Table 3-6. 8b/10b Decode Errors
RX_STATUS2-0
DETECTED ERROR
LENGTH
Clock cycles during the ef fected byte is transferred on
RX_DATA15-0
100b
8B/10B Decode Error
3.4.4 Elastic Buffer Errors
When the elastic buffer overflows, data is lost during the reception of the data. The elastic buffer overflow
error code (101b) will be asserted on the RX_STATUS on the PCLK cycle the omitted data would have
been asserted. The data asserted on the RX_DATA is still valid data, the elastic buffer overflow error code
on the RX_STATUS just marks a discontinuity point in the data stream being received.
When the elastic buffer underflows, SUB symbols are inserted into the data stream on the RX_DATA to fill
the holes created by the gaps between valid data. For every PCLK cycle a SUB symbol is asserted on the
RX_DATA, an elastic buffer underflow error code (111b) is asserted on the RX_STATUS. In Nominal
Empty buffer mode, SKP ordered sets are transferred on RX_DATA and the underflow is not signaled.
Table 3-7. Elastic Buffer Errors
RX_STATUS2-0
DETECTED ERROR
LENGTH
101b
Elastic Buffer overflow
Clock cycles the omitted data would have appeared
Clock cycles during the SUB symbol presence on
RX_DATA15-0
110b
Elastic Buffer underflow.
3.4.5 Disparity Errors
When the TUSB1310A detects a disparity error, it will assert a disparity error code (111b) on the
RX_STATUS in the same PCLK cycle it asserts the erroneous data on the RX_DATA. The disparity code
does not discern which byte on the RX_DATA is the erroneous data.
Table 3-8. Disparity Errors
RX_STATUS2-0
DETECTED ERROR
LENGTH
Clock cycles during the ef fected byte is transferred
on RX_DATA15-0
111b
Disparity Error
3.5 Loopback
The TUSB1310A begins an internal loopback operation from SSRXP/SSRXN differential pairs to
SSTXP/SSTXN differential pairs when the TX_DETRX_LPBK is asserted while holding TX_ELECIDLE
de-asserted. The TUSB1310A will stop transmitting data to the SSTXP/SSTXN signaling pair from the
TX_DATA and begin transmitting on the SSTXP/SSTXN signaling pair the data received at the
SSRXP/SSRXN signaling pair. This data is not routed through the 8b/10b coding/encoding paths. While in
the loopback operation, the received data is still sent to the RX_DATA. The data sent to the RX_DATA is
routed through the 10b/8b decoder.
The TX_DETRX_LPBK de-assertion will terminate the loopback operation and return to transmitting
TX_DATA over the SSTXP/SSTXN signaling pair. The TUSB1310A only transitions out of loopback on
detection of LFPS signaling by transitioning to P2 state and starting the LFPS handshake.
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FUNCTIONAL DESCRIPTION
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