Xilinx Virtex-6 FPGA User Manual

Virtex-6 FPGA GTX Transceivers User Guide www.xilinx.com 219
UG366 (v2.5) January 17, 2011
RX Byte and Word Alignment
on RX_DATA_WIDTH. Either a 16-bit or a 20-bit comma alignment mode is possible.
Figure 4-24 shows how the commas are combined when COMMA_DOUBLE is TRUE.
Figure 4-25 shows how COMMA_10B_ENABLE and wildcarding work for a double-width
comma.
Activating Comma Alignment
Commas are aligned to the closest boundary providing they are found while comma
alignment is active. RXENMCOMMAALIGN is driven High to align on the MCOMMA
pattern. RXENPCOMMAALIGN is driven High to activate alignment on the PCOMMA
pattern. Both enable ports are driven to align to either pattern. When COMMA_DOUBLE
is TRUE, both enable ports must always be driven to the same value.
Alignment Status Signals
While MCOMMA or PCOMMA alignment is active, any matching comma pattern causes
the block to realign to the closest boundary. After successful alignment, the block holds
RXBYTEISALIGNED High. At this time, RXENMCOMMAALIGN and
RXENPCOMMAALIGN can be driven Low to turn off alignment and keep the current
alignment position. PCOMMA_DETECT must be TRUE for PCOMMAs to cause
RXBYTEISALIGNED to go High. Similarly, MCOMMA_DETECT must be TRUE for
MCOMMAs to cause RXBYTEISALIGNED to go High. Commas can arrive while
RXBYTEISALIGNED is High. If the commas arrive aligned to boundaries, there is no
change. If the commas arrive out of position, the block deasserts RXBYTEISALIGNED
until the commas are aligned again. If alignment is still activated for the comma that
arrives, the block automatically aligns the new comma to the closest boundary and drives
RXBYTEREALIGN High for one RXUSRCLK2 cycle.
X-Ref Target - Figure 4-24
Figure 4-24: Extended Comma Pattern Definition
X-Ref Target - Figure 4-25
Figure 4-25: Extended Comma Pattern Masking
MCOMMA_10B_VALUE PCOMMA_10B_VALUE
UG366_c4_22_051509
0010100010
xx10100001
0011111111
0010100001
xx10100010
0011111111
0011111111
MCOMMA_10B_VALUE
and
PCOMMA_10B_VALUE
(COMMA_DOUBLE = TRUE)
Pattern required
for comma detection
(x = don’t care)
COMMA_10B_ENABLE
UG366_c4_23_051509
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Xilinx Virtex-6 FPGA Specifications

General

Brand	Xilinx
Model	Virtex-6 FPGA
Category	Transceiver
Language	English