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RocketIO™ Transceiver User Guide
UG024 (v3.0) February 22, 2007
Chapter 2:
Digital Design Considerations
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.
defines the
eight binary states of RXCLKCORCNT.
D0
IDLE
IDLE
IDLE
D1
D2
D0
IDLE
IDLE
IDLE
IDLE
IDLE
IDLE
D1
D2
D0
IDLE
IDLE
IDLE
IDLE
IDLE
D1
D2
Table 2-17:
RXCLKCORCNT Definition
RXCLKCORCNT[2:0]
Significance
000
No channel bonding or clock correction occurred for current
RXDATA
001
Elastic buffer skipped one clock correction sequence for
current RXDATA
010
Elastic buffer skipped two clock correction sequence for
current RXDATA
011
Elastic buffer skipped three clock correction sequence for
current RXDATA
Product Not Recommended for New Designs