Programmable Run-Length Violation Detection
The programmable run-length violation detection circuit resides in the word aligner block and detects if
consecutive 1s or 0s in the received data exceed the user-specified threshold.
If the data stream exceeds the preset maximum number of consecutive 1s or 0s, the violation is signified by
the assertion of the
rx_rlv
status bit.
Table 1-24: Detection Capabilities of the Run-Length Violation Circuit
Run-Length Violation Detector Range
PMA–PCS Interface
Width (bits)
PCS Mode
Maximum
Minimum
128
4
8
Single Width
160
5
10
512
8
16
Double Width
640
10
20
Receiver Polarity Inversion
The positive and negative signals of a serial differential link might erroneously be swapped during board
layout. Solutions such as board re-spin or major updates to the PLD logic can be expensive. The polarity
inversion feature at the receiver corrects the swapped signal error without requiring board re-spin or major
updates to the logic in the FPGA fabric. The polarity inversion feature inverts the polarity of every bit at the
input to the word aligner, which has the same effect as swapping the positive and negative signals of the
serial differential link.
Inversion is controlled dynamically with the
rx_invpolarity
register. When you enable the polarity
inversion feature, initial disparity errors may occur at the receiver with the 8B/10B-coded data. The receiver
must be able to tolerate these disparity errors.
If you enable polarity inversion midway through a word, the word will be corrupted.
Caution:
Bit Reversal
By default, the receiver assumes a LSB-to-MSB transmission. If the transmission order is MSB-to-LSB, the
receiver forwards the bit-flipped version of the parallel data to the FPGA fabric on
rx_parallel_data
.
To reverse the bit order at the output of the word aligner to receive a MSB-to-LSB transmission, use the bit
reversal feature at the receiver.
Table 1-25: Bit Reversal Feature
Received Bit Order
Bit Reversal Option
Double-Width Mode (16 or 20 bit)
Single-Width Mode (8 or 10 bit)
LSB to MSB
LSB to MSB
Disabled (default)
Altera Corporation
Transceiver Architecture in Cyclone V Devices
1-41
Programmable Run-Length Violation Detection
CV-53001
2013.05.06