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

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Clock Recovery

ENPCOMMAALIGN and ENMCOMMAALIGN are both set to zero then this signal
should not go High. See

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

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

DEC_VALID_COMMA_ONLY

DEC_PCOMMA_DETECT

DEC_MCOMMA_DETECT

PCOMMA_10B_VALUE
MCOMMA_10B_VALUE
PCOMMA_DETECT
MCOMMA_DETECT
ENPCOMMAALIGN
ENMCOMMAALIGN
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
RocketIO™ Transceiver User Guide
UG024 (v3.0) February 22, 2007
Table 2-13.
Table 2-13. If the 8B/10B decoder is bypassed, this port is undefined.
Port or Attribute
RXCHARISCOMMA
www.xilinx.com
Affects Affects
RXCOMMADET
√
√
√
Table 2-5, page 43, for details.
R
Affects Character
Alignment and
RXREALIGN
√
√
71