Xilinx 7 Series User Manual page 187

Table 4-32: RX Buffering versus Phase Alignment
Ease of Use The RX buffer is the recommended default to use
when possible. It is robust and easier to operate.
Clocking Options Can use RX recovered clock or local clock (with
clock correction).
Initialization Works immediately.
Latency Buffer latency depends on features use, such as
clock correction and channel bonding.
Clock Correction Required for clock correction and channel
and Channel bonding.
Bonding
Ports and Attributes
Table 4-33
Table 4-33: RX Buffer Ports
Port
RXBUFRESET
RXBUFSTATUS[2:0]
Table 4-34
Table 4-34: RX Buffer Attributes
Attribute
RXBUF_EN
RX_XCLK_SEL
7 Series FPGAs GTP Transceivers User Guide
UG482 (v1.9) December 19, 2016
RX Elastic Buffer
defines the RX buffer ports.
Dir Clock Domain
In Async Resets and reinitializes the RX elastic buffer.
Out RXUSRCLK2 RX buffer status.
defines the RX buffer attributes.
Type
String
String
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RX Phase Alignment
Phase alignment is an advanced feature that requires extra
logic and additional constraints on clock sources.
RXOUTCLKSEL must select the RX recovered clock as
the source of RXOUTCLK to drive RXUSRCLK.
Must use the RX recovered clock.
Must wait for all clocks to stabilize before performing the
RX phase and delay alignment procedure.
Lower deterministic latency.
Not performed inside the transceiver. Required to be
implemented in user logic.
Description
3'b000: Nominal condition.
3'b001: Number of bytes in the buffer are less than
CLK_COR_MIN_LAT
3'b010: Number of bytes in the buffer are greater than
CLK_COR_MAX_LAT
3'b101: RX elastic buffer underflow
3'b110: RX elastic buffer overflow
Description
Use or bypass the RX elastic buffer.
TRUE: Uses the RX elastic buffer (default).
FALSE: Bypasses the RX elastic buffer (advanced feature).
Selects the clock source used to drive the RX parallel clock domain
(XCLK).
RXREC: Selects the RX recovered clock as the source of XCLK.
Used when using the RX elastic buffer.
RXUSR: Selects RXUSRCLK as the source of XCLK. Used
when bypassing the RX elastic buffer.
RX Elastic Buffer
187
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