This Answer Record provides answers to SONET Frequently Asked Questions (FAQs).
Q1: What is the correct bit/byte ordering when using the Virtex-4 RocketIO in a SONET application?
A1: In a SONET application, the bit/byte ordering is completely reversed because SONET requires the MSB to be transmitted first. The Virtex-4 transceiver transmits LSB first. Consequently, the traditional SONET TXDATA [63:0] is byte-mapped to TXDATA[0:63] in the Virtex-4 RocketIO.
Q2: What is the correct COMMA_32B_VALUE for a SONET application?
A2: Since the transmission bit ordering for SONET is reversed as compared to other standards,
PCOMMA_32B_VALUE = 32'h6F6F1414 (the bit flip of 32'hF6F62828).
MCOMMA_32B_VALUE = 32'hXXXXX6F