CertusPro-NX SerDes/PCS Usage Guide
Preliminary
Technical Note
44
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Signal Name
Description
Once de-asserted, the 64-bit data and 8-bit control are encoded and scrambled before they go to Tx
Gear Box.
1'b1 – on the same cycle, use 64-bit data and 2-bit header coming from user logic to feed the
Gear Box.
1'b0 – process the 64-bit data and 8-bit control as normal (go through encoder, scrambler, and
gear box).
tx_fifo_wr
Write 64-bit data and 8-bit control to Tx FIFO. User logic should monitor the FIFO status and properly
control the writing operation to avoid the FIFO overflow or underflow.
tx_fifo_status[3:0]
Tx FIFO status:
bit[0] – FIFO is almost empty.
bit[1] – FIFO is almost full.
bit[2] – FIFO underflow.
bit[3] – FIFO overflow.
Receive Status Signals
rx_control[7:0]/
rx_header[1:0]
8-bit control indication:
bit[0] – the control signal for rx_data_64b[7:0].
bit[1] – the control signal for rx_data_64b[15:8].
…
bit[7] – the control signal for rx_data_64b[63:56].
In 64B/66B decoder bypass mode, bit[1:0] of this signal is used to carry rx_header[1:0] of a 66-bit
block. Other bits are not used in this mode.
rx_fifo_add[1:0]
The indication of insertion for clock frequency difference compensation:
bit[1] – corresponds to 4-byte idles which are carried by bit[63:32] of data bus (rx_data_64b).
bit[0] – corresponds to 4-byte idles which are carried by bit[31:0] of data bus (rx_data_64b).
rx_fifo_del[1:0]
The indication of deletion for clock frequency difference compensation:
bit[1] – corresponds to 4-byte idles or sequence ordered-set which are carried by bit[63:32] of
data bus (rx_data_64b).
bit[0] – corresponds to 4-byte idles or sequence ordered-set which are carried by bit[31:0] of data
bus (rx_data_64b).
rx_data_valid
Output indicator:
1’b1 – the output data is valid.
1’b0 – no valid data on the output of Rx FIFO.
rx_fifo_status[3:0]
Rx FIFO status:
bit[0] – FIFO is almost empty.
bit[1] – FIFO is almost full.
bit[2] – FIFO underflow.
bit[3] – FIFO overflow.
Detailed Channel Block Diagram
Detailed block diagrams in this section are intended to show you the major functionality in a single channel of the
CertusPro-NX SerDes/PCS. You can find all the major blocks, clock, and data flow in these diagrams. PCI Express PCS
channel is hidden in all the three modes, considering that this channel can only be used by PCI Express protocol.
MPCS-8B/10B Mode
is the detailed channel block diagram of MPCS-8B/10B mode. In this mode, only 8B/10B PCS channel is
expanded. 64B/66B PCS channel and PMA Only channel are hidden.