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CYP15G0401DXA
PRELIMINARY
Document #: 38-02002 Rev. *B
Page 28 of 48
Receive Synchronization State Machine
Each receive channel contains a Receive Synchronization
state machine. This machine handles loss and recovery of bit,
channel, and word framing, and part of the control for channel
bonding. This state machine is enabled whenever the receive
channels are configured for channel bonding (RXMODE[1]
≠
LOW). Separate forms of the state machine exist for the two
different types of status reporting.
When operated without channel bonding (RXMODE[1] = LOW,
RX Modes 0 and 2), these state machines are disabled and
characters are decoded directly. In RX Mode 0 the
RESYNC (111b) status is never reported. In RX Mode 2, nei-
ther the RESYNC (111b) or Channel Lock Detected (010b)
status are reported.
Table 21. Receive Character Status Bits
RXSTx[2:0] Priority
000
Description
Type-A Status
Normal Character Received.
The valid Data character on the output
bus meets all the formatting requirements of Data characters listed in
Table 24
.
Special Code Detected.
The valid special character on the output bus
meets all the formatting requirements of Special Code characters listed
in
Table 25
, but is not the presently selected framing character or a de-
coder violation indication.
Receive Elasticity Buffer Under-
run/Overrun Error.
The receive
buffer was not able to add/drop a
K28.5 or framing character.
Type-B Status
Receive BIST Status
(Receive BIST = Enabled)
BIST Data Compare.
Charac-
ter compared correctly
7
001
7
BIST Command Compare.
Character compared correctly
010
2
Channel Lock Detected.
Asserts
when the bonded channels have
detected RESYNC within the allot-
ted window. Presented only on the
last cycle before aligned data is pre-
sented.
BIST Last Good.
Last Charac-
ter of BIST sequence detected
and valid.
011
5
Framing Character detected.
This indicates that a character matching
the patterns identified as a framing character (as selected by
FRAMCHAR) was detected. The decoded value of this character is
present in the associated output bus.
Codeword Violation.
The character on the output bus is a C0.7. This
indicates that the received character cannot be decoded into any valid
character.
Loss of Sync.
The character on
the bus is invalid, due to an event
that has caused the receive chan-
nels to lose synchronization. When
channel bonding is enabled, this in-
dicates that one or more channels
have either lost bit synchronization
(loss of character framing), or that
the bonded channels are no longer
in proper character alignment.
When the channels are operated in-
dependently (with the decoder en-
abled), this indicates a PLL Out of
Lock condition.
100
4
BIST Last Bad.
Last Character
of BIST sequence detected in-
valid.
BIST Start.
Receive BIST is en-
abled on this channel, but char-
acter compares have not yet
commenced. This also indi-
cates a PLL Out of Lock condi-
tion, and Elasticity Buffer over-
flow/underflow conditions.
101
1
Loss of Sync.
The character on
the bus is invalid, due to an event
that has caused the receive chan-
nels to lose synchronization. When
channel bonding is enabled, this in-
dicates that one or more channels
have either lost bit synchronization
(loss of character framing), or that
the bonded channels are no longer
in proper character alignment.
When the channels are operated in-
dependently (with the decoder en-
abled), this indicates a loss of char-
acter framing. Also used to indicate
receive Elasticity Buffer under-
flow/overflow errors.
110
6
Running Disparity Error.
The character on the output bus is a C4.7,
C1.7, or C2.7.
BIST Error.
While comparing
characters, a mismatch was
found in one or more of the de-
coded character bits.
BIST Wait.
The receiver is com-
paring characters. but has not
yet found the start of BIST char-
acter to enable the LFSR.
111
3
Resync.
The receiver state machine is in the Resynchronization state.
In this state the data on the output bus reflects the presently decoded
FRAMCHAR.