Dec_Pcomma_Detect; Dec_Mcomma_Detect; Dec_Valid_Comma_Only; Rxchariscomma - Xilinx RocketIO User Manual

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RXCHARISCOMMA

This signal is similar to RXCHARISK, except that it signals that a specific byte of RXDATA is a
comma character. However, this definition only holds true for when 8B/10B encoding/decoding is
enabled. This port is controlled by the DEC_* attributes and is shown in
decoder is bypassed, this port is undefined.

RXCOMMADET

This signal indicates if a comma character has been detected in the serial data. The definition of this
port is defined by the PCOMMA_DETECT and MCOMMA_DETECT attributes. This signal is
clocked off RXRECCLK, and to reliably have the signal pulse for all the data width configurations,
this pulse may change with respect to the USRCLKs.
Table 2-13: Effects of Comma-Related Ports and Attributes

Clock Recovery

Overview

Clock Synthesizer

Synchronous serial data reception is facilitated by a clock/data recovery circuit. This circuit uses a
fully monolithic Phase-Locked Loop (PLL), which does not require any external components. The
clock/data recovery circuit extracts both phase and frequency from the incoming data stream. The
recovered clock is presented on output RXRECCLK at 1/20 of the serial received data rate.
The gigabit transceiver multiplies the reference frequency provided on the reference clock input
(REFCLK) by 20.
No fixed phase relationship is assumed between REFCLK, RXRECCLK, and/or any other clock
that is not tied to either of these clocks. When the 4-byte or 1-byte receiver data path is used,
RXUSRCLK and RXUSRCLK2 have different frequencies (1:2), and each edge of the slower clock
is aligned to a falling edge of the faster clock. The same relationships apply to TXUSRCLK and
TXUSRCLK2. See

Clock and Data Recovery

The clock/data recovery (CDR) circuits lock to the reference clock automatically if the data is not
present. For proper operation, TXUSRCLK must have the exact same frequency as REFCLK.
72
Port or Attribute

DEC_VALID_COMMA_ONLY

DEC_PCOMMA_DETECT

DEC_MCOMMA_DETECT

PCOMMA_10B_VALUE
MCOMMA_10B_VALUE
PCOMMA_DETECT
MCOMMA_DETECT
ENPCOMMAALIGN
ENMCOMMAALIGN
Table 2-5, page
www.xilinx.com
1-800-255-7778
Chapter 2: Digital Design Considerations
Affects
RXCHARISCOMMA RXCOMMADET
√
43, for details.
RocketIO™ Transceiver User Guide
Table 2-13. If the 8B/10B
Affects Character
Affects
Alignment and
RXREALIGN
√ √
√
√
UG024 (v2.3.2) June 24, 2004