| AR# |
21763 |
| Part |
HW-Rocket_IO |
| Last Modified |
2008-05-19 00:00:00.0 |
| Status |
Active |
| Keywords |
COMMA32, Frequently Asked Questions |
Description
Keywords: COMMA32, Frequently Asked Questions
This Answer Record provides answers to SONET Frequently Asked Questions (FAQs).
Solution
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
