Rxlossofsync - Xilinx RocketIO User Manual

R

RXLOSSOFSYNC

If RX_LOSS_OF_SYNC_FSM = FALSE, then RXLOSSOFSYNC[1] High indicates that the
transceiver has received an invalid character, and RXLOSSOFSYNC[0] High indicates that a
channel-bonding sequence has been recognized.
If RX_LOSS_OF_SYNC_FSM = TRUE, then the two bits of RXLOSSOFSYNC reflect the state of
the RXLOSSOFSYNC FSM. The state machine diagram in
following describe the three states of the RXLOSSOFSYNC FSM.
SYNC_ACQUIRED (RXLOSSOFSYNC = 00)
In this state, a counter is decremented by 1 (but not past 0) for a valid received symbol and
incremented by RX_LOS_INVALID_INCR for an invalid symbol. If the count reaches or exceeds
RX_LOS_THRESHOLD, the FSM moves to state LOSS_OF_SYNC. Otherwise, if a channel
bonding (alignment) sequence has just been written into the elastic buffer, or if a comma
realignment has just occurred, the FSM moves to state RESYNC. Otherwise, the FSM remains in
state SYNC_ACQUIRED.
RESYNC (RXLOSSOFSYNC = 01)
The FSM waits in this state for four RXRECCLK cycles and then goes to state SYNC_ACQUIRED,
unless an invalid symbol is received, in which case the FSM goes to state LOSS_OF_SYNC.
LOSS_OF_SYNC (RXLOSSOFSYNC = 10)
The FSM remains in this state until a comma is received, at which time it goes to state RESYNC.
78
valid data + 4 RXRECCLK cycles
valid data + < 4 RXRECCLK cycles
Figure 2-21: RXLOSSOFSYNC FSM States
1-800-255-7778
Chapter 2: Digital Design Considerations
SYNC_ACQUIRED
00
channel alignment
comma realignment
invalid data
01
RESYNC
comma received
www.xilinx.com
Figure 2-21 and the three subsections
count < RX_LOS_THRESHOLD
count = RX_LOS_THRESHOLD
or
no comma received
10
LOSS_OF_SYNC
UG024_40_031803
RocketIO™ Transceiver User Guide
UG024 (v2.3.2) June 24, 2004