Xilinx RocketIO User Manual

70 www.xilinx.com RocketIO™ Transceiver User Guide
UG024 (v3.0) February 22, 2007
Chapter 2: Digital Design Considerations
R
PCOMMA_DETECT,
MCOMMA_DETECT
These two control attributes define when RXCOMMADET signals that a comma has been
received. When only PCOMMA_DETECT is TRUE, RXCOMMADET signals when a plus-
comma is received, but not a minus-comma. When only MCOMMA_DET is TRUE,
RXCOMMADET signals when a minus-comma is received, but not a plus-comma. If both
attributes are TRUE, RXCOMMADET will signal when either comma character is received.
COMMA_10B_MASK,
PCOMMA_10B_VALUE,
MCOMMA_10B_VALUE
The RocketIO transceiver allows the user to define a comma character using these three
attributes. The COMMA_10B_MASK bits are used in conjunction with
PCOMMA_10B_VALUE (to define a plus-comma) or MCOMMA_10B_VALUE (to define a
minus-comma) to define some number of recognized comma characters. High bits in the
mask condition the corresponding bits in PCOMMA_10B_VALUE or
MCOMMA_10B_VALUE to matter, while Low bits in the mask function as a “don’t care”
conditioner.
For example, with COMMA_10B_MASK set to 1111111000 (meaning the three least
significant bits don’t matter) and PCOMMA_10B_VALUE is 0011111000, the comma
detection unit will recognize the following characters as plus-commas:
0011111000 (K28.7)
0011111001 (K28.1)
0011111010 (K28.5)
0011111011 through 0011111111 (not valid comma characters)
Using the same value in PCOMMA_10B_VALUE but setting COMMA_10B_MASK to
1111111111 (meaning all the bits in PCOMMA_10B_VALUE matter), the comma
detection unit will recognize only the 0011111000 (K28.7) sequence, which matches the
value of PCOMMA_10B_VALUE exactly.
DEC_PCOMMA_DETECT,
DEC_MCOMMA_DETECT,
DEC_VALID_COMMA_ONLY
These signals only pertain to the 8B/10B decoder, not the comma alignment circuitry. The
DEC_PCOMMA_DETECT and DEC_MCOMMA_DETECT control the 8B/10B decoder to
signal the RXCHARISCOMMA port if a plus-comma or minus-comma is received. This is
described in the table below.
DEC_VALID_COMMA_ONLY, for most applications, should be set to TRUE. If valid data
is being transmitted and hence received, then an invalid comma would arise only in the
case of a bit error, in which case RXCHARISCOMMA would not be asserted in the
presence of bit errors. If set to FALSE, then RXCHARISCOMMA will be asserted for
invalid K-characters.
RXREALIGN
This status signal indicates whenever, the serial data is realigned from a comma character
in the data stream. This signal will not necessarily go High after the transceiver is reset. If
Product Not Recommended for New Designs

Xilinx RocketIO Specifications

General

Brand	Xilinx
Model	RocketIO
Category	Transceiver
Language	English