Activating Comma Alignment; Alignment Status Signals; Alignment Boundaries - Xilinx Virtex-5 RocketIO GTP User Manual

R
Figure 7-14
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 should 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_ALIGN must be TRUE for PCOMMAs to cause
RXBYTEISALIGNED to go High. Similarly, MCOMMA_ALIGN 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.

Alignment Boundaries

The legal boundaries for alignment are defined by ALIGN_COMMA_WORD. The spacing
of the legal boundaries is determined by INTDATAWIDTH, and the number of legal
boundary positions is determined by the number of bytes in the RXDATA interface.
Figure 7-15
Virtex-5 RocketIO GTP Transceiver User Guide
UG196 (v1.3) May 25, 2007
shows how COMMA_10B_ENABLE and wildcarding work for a double-width
MCOMMA_10B_VALUE
and
PCOMMA_10B_VALUE
(COMMA_DOUBLE = TRUE)
0010100001 0010100010
0011111111 0011111111
0011111111
COMMA_10B_ENABLE
Figure 7-14: Extended Comma Pattern Masking
shows the boundaries that can be selected.
www.xilinx.com
Configurable Comma Alignment and Detection
for comma detection
xx10100001
Pattern required
(x = don't care)
xx10100010
UG196_c7_14_092606
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