Xilinx Virtex-5 RocketIO GTP, User Manual

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138 www.xilinx.com Virtex-5 RocketIO GTP Transceiver User Guide
UG196 (v1.3) May 25, 2007
Chapter 7: GTP Receiver (RX)
R
CDR Reset
The CDR must be reset before it can operate on incoming data. There are several ways to
reset the CDR:
•
Use the GTPRESET port to reset all components in the GTP_DUAL tile, including the
CDR in each transceiver. See
“Reset,” page 72 for more details.
•
Use the RXCDRRESET port to reset the CDR block, the OOB circuits for SATA (see
“RX OOB/Beacon Signaling,” page 129 ), the RX buffer (see “Configurable RX Elastic
Buffer and Phase Alignment,” page 161 ), and the remaining sections of the RX PCS.
•
Use the RXELECIDLERESET and RXENELECIDLERESETB ports, which are part of
the Link Idle Reset described in
“Reset,” page 72 . The Link Idle Reset circuit must be
implemented whenever a GTP receiver is used. The RXENELECIDLERESET port
enables the RXELECIDLE RESET port, which is used to reset the CDR without
resetting any other blocks in response to electrical idle conditions.
Figure 7-5 shows the timing of the internal reset signals when RXCDRRESET is asserted.
RXCDRRESET can be asserted asynchronously. When it is asserted, an internal CDR reset
pulse, synchronized to an internally generated 1 MHz clock, resets the CDR. Similarly, a
reset pulse is generated for the SATA OOB circuit (internal SATA reset), the RX PCS
datapath (internal RXRESET), and the RX buffer (internal RXBUFRESET). The entire
sequence completes in approximately 5 µs.
Figure 7-5: Reset Sequence Triggered by RXCDRRESET
RXCDRRESET
Internal CDR Reset
Internal SATA Reset
Internal RXRESET
Internal RXBUFRESET
Asynchrono u s P u lse
Internal 1 MHz Clock
High for at least 2
μ
s
High for 1
μ
s
Deasserts 1
μ
s later
Deasserts 1
μ
s later
Total Reset time ~ 5
μ
s
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