User guide

Figure 2-97: Word Aligner in Deterministic Mode Waveform
rx_clkout
rx_std_wa_patternalign
rx_parallel_data
rx_errdetect
rx_disperr
rx_patterndetect
rx_syncstatus
f1e4b6e4
1101
1101
0000
0000
0000
0000
1010
1010
1000
1000
0010
0000
1010
1010
0000
0000
1111
1111
0000
b9dbf1db 915d061d e13f913f 7a4ae24a bbae9b10 bcbcbcbc 95cd3c50 91c295cd
Related Information
Word Aligner on page 5-42
Transmitter and Receiver Latency
The latency variation from the link synchronization function (in the word aligner block) is deterministic
with the rx_bitslipboundaryselectout port. Additionally, you can use the tx_bitslipboundaryse-
lect port to fix the round trip transceiver latency for port implementation in the remote radio head to
compensate for latency variation in the word aligner block. The tx_bitslipboundaryselect port is
available to control the number of bits to be slipped in the transmitter serial data stream. You can
optionally use the tx_bitslipboundaryselect port to round the round-trip latency to a whole number
of cycles.
When using the byte deserializer, additional logic is required in the FPGA fabric to determine if the
comma byte is received in the lower or upper byte of the word. The delay is dependent on the word in
which the comma byte appears.
The total transmitter and receiver channel datapath latencies are computed as follows:
• The total transmitter channel datapath latency is equal to the transmitter fixed latency and
tx_bitslipboundaryselect delay.
• The total receiver channel datapath latency is equal to the receiver fixed latency, rx_std_bitslip-
boundarysel delay, and byte deserializer delay.
Note:
Latency numbers are pending device characterization.
Word Aligner in Manual Mode for CPRI
When configuring the word aligner in CPRI (Manual), the word aligner parses the incoming data stream
for a specific alignment character. After rx_digitalreset deasserts, asserting the
rx_std_wa_patternalign triggers the word aligner to look for the predefined word alignment pattern or
its complement in the received data stream. It is important to note that the behavior of the word aligner in
Manual mode operates in different ways depending on the PCS-PMA interface width.
UG-01143
2015.05.11
Transmitter and Receiver Latency
2-271
Implementing Protocols in Arria 10 Transceivers
Altera Corporation
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