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fpga: x400: pps_sync cleanup

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Original-commit: 4527a8f70d35d88f8cd75dd358fff07f29496f4f
This commit is contained in:
Javier Valenzuela
2023-10-17 10:18:17 -05:00
committed by Wade Fife
parent 4e26d6946f
commit 4d38451f2a
1 changed files with 37 additions and 34 deletions
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top/x400/x4xx_pps_sync.v
+36 -33
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@@ -44,7 +44,7 @@ module x4xx_pps_sync #(
output wire pll_sync_done,
input wire [7:0] pps_brc_delay,
input wire [25:0] pps_prc_delay,
input wire [3:0] prc_rc_divider,
input wire [9:0] prc_rc_divider,
input wire pps_rc_enabled,
//signal for debugging
@@ -363,6 +363,11 @@ module x4xx_pps_sync #(
always @(posedge pll_ref_clk) begin
// Disable delayed rising edge by default
pps_delayed_prc <= 1'b0;
// pps_delayed_prc should assert one PRC clock cycle before the aligned edge,
// so that it can be transferred to the radio clock domain when PRC and radio_clock
// run at the same rate. pps_delayed_prc_out holds the PPS on PRC domain delayed to
// the aligned edge.
pps_delayed_prc_out <= pps_delayed_prc;
pps_prc_delayed <= pps_prc;
// Reset counter on rising edge
@@ -386,21 +391,28 @@ module x4xx_pps_sync #(
// rc. The divider has to account for the output register and the shift
// register.
wire [3:0] prc_rc_divider_rc;
wire [1:0] pps_rc_enabled_rc;
wire [1:0] pps_delayed_prc_rc;
reg [7:0] pps_shift_reg_rc = 8'b0;
genvar rc_sync_i;
generate
for (rc_sync_i = 0; rc_sync_i < 2; rc_sync_i = rc_sync_i+1) begin : gen_rc_sync
synchronizer #(
.FALSE_PATH_TO_IN (1),
.WIDTH (2)
wire [ 4:0] prc_rc_divider_rc;
reg [ 4:0] prc_rc_divider_reg_rc = 5'b0;
wire prc_rc_divider_valid;
wire pps_rc_enabled_rc;
// Make signal one bit longer than maximum divider value to enable t-1 comparison.
reg [31:0] pps_shift_reg_rc = 32'b0;
handshake #(
.WIDTH (5)
) synchronizer_prc_rc_divider (
.clk (radio_clk[rc_sync_i]),
.rst (1'b0),
.in (prc_rc_divider[2*rc_sync_i+:2]),
.out (prc_rc_divider_rc[2*rc_sync_i+:2])
.clk_a (ctrl_clk),
.rst_a (1'b0),
.valid_a (1'b1),
.data_a (prc_rc_divider[5*rc_sync_i+:5]),
.busy_a (),
.clk_b (radio_clk[rc_sync_i]),
.valid_b (prc_rc_divider_valid),
.data_b (prc_rc_divider_rc)
);
synchronizer #(
.FALSE_PATH_TO_IN (1)
@@ -408,31 +420,22 @@ module x4xx_pps_sync #(
.clk (radio_clk[rc_sync_i]),
.rst (1'b0),
.in (pps_rc_enabled),
.out (pps_rc_enabled_rc[rc_sync_i])
);
synchronizer #(
.FALSE_PATH_TO_IN (1)
) synchronizer_pps_rc (
.clk (radio_clk[rc_sync_i]),
.rst (1'b0),
.in (pps_delayed_prc),
.out (pps_delayed_prc_rc[rc_sync_i])
.out (pps_rc_enabled_rc)
);
always @(posedge radio_clk[rc_sync_i]) begin
if (prc_rc_divider_valid) begin
prc_rc_divider_reg_rc <= prc_rc_divider_rc;
end
pps_shift_reg_rc <= {pps_shift_reg_rc[30:0], pps_delayed_prc};
// Restoring a one clock cycle pulse by feeding back to output value.
pps_out_rc[rc_sync_i] <= pps_shift_reg_rc[prc_rc_divider_reg_rc] &
~pps_shift_reg_rc[prc_rc_divider_reg_rc+1] & pps_rc_enabled_rc;
end
end
endgenerate
always @(posedge radio_clk[0]) begin
pps_shift_reg_rc[3:0] <= {pps_shift_reg_rc[2:0], pps_delayed_prc};
// Restoring a one clock cycle pulse by feeding back to output value.
pps_out_rc[0] <= pps_shift_reg_rc[prc_rc_divider_rc[1:0]] & ~pps_out_rc[0] & pps_rc_enabled_rc[0];
end
always @(posedge radio_clk[1]) begin
pps_shift_reg_rc[7:4] <= {pps_shift_reg_rc[6:4], pps_delayed_prc};
// Restoring a one clock cycle pulse by feeding back to output value.
pps_out_rc[1] <= pps_shift_reg_rc[prc_rc_divider_rc[3:2]] & ~pps_out_rc[1] & pps_rc_enabled_rc[1];
end
//---------------------------------------------------------------------------
// Debug assignment
//---------------------------------------------------------------------------