Synchronization Logic; Overview; Ports And Attributes; Rxclkcorcnt - Xilinx RocketIO User Manual

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R
clock correction must occur before another clock correction sequence can occur. If this
attribute is 0, no limit is placed on how frequently clock correction can occur.
Example: Elastic buffer is 25% full, clock correction is needed, and one sequence is repeated
per clock correction. (IDLE is the defined clock correction sequence.)
Data stream written into elastic buffer:
Data stream read out of elastic buffer (CLK_COR_REPEAT_WAIT = 0):
Data stream read out of elastic buffer (CLK_COR_REPEAT_WAIT = 1):
The percent that the buffer is full, together with the value of CLK_COR_REPEAT_WAIT,
determines how many times the clock correction sequence is repeated during each clock
correction.

Synchronization Logic

Overview

For some applications, it is beneficial to know if incoming data is valid or not, and if the
MGT is synchronized on the data. For applications using the 8B/10B encoding scheme, the
RX_LOSS_OF_SYNC FSM does this. It can be programmed to lose sync after a specified
number of invalid data characters are received.

Ports and Attributes

RXCLKCORCNT

Clock correction count (RXCLKCORCNT) is a three-bit signal. It signals if clock correction
has occurred, and whether the elastic buffer realigned the data by skipping or repeating
data in the buffer. It also signals if channel bonding has occurred.
eight binary states of RXCLKCORCNT.
Table 2-17: RXCLKCORCNT Definition
76
D0 IDLE IDLE
D0 IDLE IDLE
D0 IDLE IDLE
RXCLKCORCNT[2:0]
No channel bonding or clock correction occurred for current
000
RXDATA
Elastic buffer skipped one clock correction sequence for
001
current RXDATA
Elastic buffer skipped two clock correction sequence for
010
current RXDATA
Elastic buffer skipped three clock correction sequence for
011
current RXDATA
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Chapter 2: Digital Design Considerations
IDLE D1 D2
IDLE IDLE IDLE
IDLE IDLE IDLE
Significance
RocketIO™ Transceiver User Guide
IDLE D1 D2
D1 D2
Table 2-17 defines the
UG024 (v3.0) February 22, 2007