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am_tx.v
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am_tx.v
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/* Copyright (c) 2023, Julia Desmazes. All rights reserved.
*
* This work is licensed under the Creative Commons Attribution-NonCommercial
* 4.0 International License.
*
* This code is provided "as is" without any express or implied warranties. */
/* Add alignement marker on tx pipe */
module am_tx #(
parameter LANE_N = 4,
parameter HEAD_W = 2,
parameter DATA_W = 64,
parameter [DATA_W-1:0]
// 0x90, 0x76, 0x47, BIP3 , 0x6F, 0x89, 0xB8, BIP7
MARKER_LANE0 = { {8{1'bx}}, 8'hb8, 8'h89, 8'h6f, {8{1'bx}}, 8'h47, 8'h76, 8'h90 },
// 0xF0, 0xC4, 0xE6, BIP3 , 0x0F, 0x3B, 0x19, BIP7
MARKER_LANE1 = { {8{1'bx}}, 8'h19, 8'h3b, 8'h0f, {8{1'bx}}, 8'he6, 8'hc4, 8'hf0 },
// 0xC5, 0x65, 0x9B, BIP3 , 0x3A, 0x9A, 0x64, BIP7
MARKER_LANE2 = { {8{1'bx}}, 8'h64, 8'h9a, 8'h3a, {8{1'bx}}, 8'h9b, 8'h65, 8'hc5 },
// 0xA2, 0x79, 0x3D, BIP3 , 0x5D, 0x86, 0xC2, BIP7
MARKER_LANE3 = { {8{1'bx}}, 8'hc2, 8'h86, 8'h5d, {8{1'bx}}, 8'h3d, 8'h79, 8'ha2 },
parameter [LANE_N*DATA_W-1:0] MARKER_LANE={ MARKER_LANE3, MARKER_LANE2, MARKER_LANE1, MARKER_LANE0}
)
(
input clk,
input nreset,
/* Gearbox */
input valid_i, /* accept data this cycle */
output [LANE_N*HEAD_W-1:0] head_o,
output [LANE_N*DATA_W-1:0] data_o,
/* Encoder */
input [LANE_N*HEAD_W-1:0] head_i,
/* Scrambler */
input [LANE_N*DATA_W-1:0] data_i,
output marker_v_o
);
localparam GAP_W = 14;
// number of cycles since last alignement marker
// count 16383 blocks between 2 makrets
// which is equivalent to the overflow on 14 bits
reg [GAP_W-1:0] gap_q;
logic [GAP_W-1:0] gap_next;
logic [GAP_W-1:0] gap_add;
logic unused_gap_add_of;
assign { unused_gap_add_of, gap_add } = gap_q + {{GAP_W-1{1'b0}}, 1'b1};
assign gap_next = gap_add;
logic add_market_v_next;
reg add_market_v_q;
// alginement marker is inserted every 16383 blocks's
// 16383 = 2^14 - 1
assign add_market_v_next = &gap_q;
always @(posedge clk) begin
if ( ~nreset ) begin
// reset to 1 by default as 0 is the cycle were we
// insert the aligment marker
gap_q <= {{GAP_W-1{1'b0}}, 1'b1};
add_market_v_q <= 1'b0;// don't add alignement market on reset
end else if ( valid_i ) begin
gap_q <= gap_next;
add_market_v_q <= add_market_v_next;
end
end
genvar i;
generate
for( i = 0; i < LANE_N; i++) begin : gen_am_lane_loop
logic [DATA_W-1:0] data;
logic [HEAD_W-1:0] head;
logic [DATA_W-1:0] data_m;
logic [HEAD_W-1:0] head_m;
assign data = data_i[i*DATA_W+DATA_W-1:i*DATA_W];
assign head = head_i[i*HEAD_W+HEAD_W-1:i*HEAD_W];
assign data_o[i*DATA_W+DATA_W-1:i*DATA_W] = data_m;
assign head_o[i*HEAD_W+HEAD_W-1:i*HEAD_W] = head_m;
am_lane_tx #(.LANE_ENC(MARKER_LANE[i*DATA_W+DATA_W-1:i*DATA_W]))
m_market_lane(
.clk(clk),
.nreset(nreset),
.marker_v(add_market_v_q),
.valid_i(valid_i),
.data_i({ data , head }),
.data_o({ data_m, head_m })
);
end
endgenerate
assign marker_v_o = add_market_v_q;
`ifdef FORMAL
always @(posedge clk) begin
if( nreset ) begin
// aligmenent marker added on sequence cnt 2^14 ( overlow )
sva_marker_2_pow_14 : assert( ~marker_v_o | marker_v_o & gap_add_overflow );
sva_marker_gap_zero : assert( ~marker_v_o | marker_v_o & ( gap_q == 0 ) );
end
end
`endif
endmodule