Arria® V Device Handbook: Volume 2: Transceivers

ID 683573
Date 5/29/2020
Document Table of Contents Receiver Byte Reversal

The two symbols of incoming data at the receiver in double-width mode may be accidentally swapped during transmission.

For a 16-bit input data width at the word aligner, the two symbols are bits[15:8] and bits[7:0]. For a 20-bit input data width at the word aligner, the two symbols are bits[19:10] and bits[9:0]. The byte reversal feature at the word aligner output can correct this error by swapping the two symbols in double-width mode at the word aligner output.

Table 30.  Byte Reversal Feature
Byte Reversal Option Word Aligner Output
16-bit Data Width 20-bit Data Width
Disabled D[15:0] D[19:0]
Enabled D[7:0], D[15:8] D[9:0], D[19:10]

The reversal is controlled dynamically using the rx_bytereversal_enable register. Enabling the byte reversal option may cause initial disparity errors at the receiver with 8B/10B-coded data. The receiver must be able to tolerate these disparity errors.

Note: When receiving swapped symbols, the word alignment pattern must be byte-reversed to match the incoming byte-reversed data.