When the RS-FEC is enabled in the receive direction, data received by the GTM PMA and PCS is
passed to the Integrated KP4 RS-FEC. The RS-FEC then aligns and deskews the input lanes
according to the configured mode to reconstruct the transmitted RS codeword stream. The RS-
FEC then performs RS decoding according to the 802.3bj clause 91 specification. The decoded
output data from the Integrated KP4 RS-FEC is then presented on the output of the GTM
transceiver to the fabric.
The Integrated KP4 RS-FEC does not natively perform transcoding, alignment marker removal,
alignment marker mapping, or alignment marker insertion operations in the receive directions. To
support protocols such as 100G Ethernet (IEEE 802.3 clause 91) and 50G Ethernet (IEEE 802.3
clause 134) which require 257b transcoding and alignment marker processing, the GTM Wizard
IP can optionally include soft logic blocks for these functions.
Ports and Attributes
The following table shows the RX FEC-related ports for the GTM dual.
Table 66: RX FEC Ports
Ports
Dir
Clock Domain
Description
CH[0/1]_RXFECRESET
In
Async
Component reset port for RX FEC.
CH[0/1]_RXDATA[159:0]
Out
CH[0/1]_RXUSRCLK2
Output RX data. Must use 160-bit interface
when FEC is enabled.
CH[0/1]_RXDATASTART
Out
CH[0/1]_RXUSRCLK2
Start of codeword.
CH[0/1]_RXDATAISAM
Out
CH[0/1]_RXUSRCLK2
Alignment marker flag.
CH[0/1]_RXDATAFLAG[3:0]
Out
CH[0/1]_RXUSRCLK2
Codeword status flags:
Bit 0: When High, indicates the codeword
input to the decoder has no errors.
Bit 1: When High, indicates the codeword
input to the decoder has errors.
Bit 2: When High, indicates the codeword
output from the decoder has no errors.
Bit 3: When High, indicates the codeword
output from the decoder has errors.
FECCTRLRX0BITSLIPFS
In
CH0_RXUSRCLK2
Bitslip control for slice 0.
FECCTRLRX1BITSLIPFS
In
CH1_RXUSRCLK2
Bitslip control for slice 1.
FECRX0ALIGNED
Out
CH0_RXUSRCLK2
Slice 0 alignment status.
FECRX1ALIGNED
Out
CH1_RXUSRCLK2
Slice 1 alignment status.
FECRX0CWINC
Out
CH0_RXUSRCLK2
Slice 0 codeword count increment.
FECRX1CWINC
Out
CH1_RXUSRCLK2
Slice 1 codeword count increment.
FECRX0CORRCWINC
Out
CH0_RXUSRCLK2
Slice 0 corrected codeword count increment.
FECRX1CORRCWINC
Out
CH1_RXUSRCLK2
Slice 1 corrected codeword count increment.
FECTRXLN0LOCK
Out
CH0_RXUSRCLK2
Lane 0 lock status.
FECTRXLN1LOCK
Out
CH0_RXUSRCLK2
Lane 1 lock status.
FECTRXLN2LOCK
Out
CH1_RXUSRCLK2
Lane 2 lock status.
Chapter 4: Receiver
UG581 (v1.0) January 4, 2019
Virtex Ult GTM Transceivers
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