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axi_adc_trigger: Fix two sample offset 

When using a non-maximum sampling rate the data is captured earlier by two
samples.
After the initial trigger jitter fix, a low latency/utilization was
desired(one sample delay for the trigger detection). After adding the
instrument trigger an equal latency between ADC and LA was required, hence the
need for a two sample delay on the trigger path. The delay was implemented
as two clock cycle delays not two sample delays.
This commit fixes this issue and offers a more robust design.
main
AndreiGrozav 2019-11-18 11:25:25 +02:00 committed by AndreiGrozav
parent d844167850
commit e0813d49b6
1 changed files with 72 additions and 42 deletions
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94
library/axi_adc_trigger/axi_adc_trigger.v
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@ -137,10 +137,6 @@ module axi_adc_trigger #(
wire comp_low_a_s; // signal is over the limit
wire comp_low_b_s; // signal is over the limit
wire passthrough_high_a_s; // trigger when rising through the limit
wire passthrough_low_a_s; // trigger when fallingh thorugh the limit
wire passthrough_high_b_s; // trigger when rising through the limit
wire passthrough_low_b_s; // trigger when fallingh thorugh the limit
wire trigger_a_fall_edge;
wire trigger_a_rise_edge;
wire trigger_b_fall_edge;
@ -164,16 +160,20 @@ module axi_adc_trigger #(
reg trigger_b_d3;
reg comp_high_a; // signal is over the limit
reg old_comp_high_a; // t + 1 version of comp_high_a
reg first_a_h_trigger; // valid hysteresis range on passthrough high trigger limit
reg first_a_l_trigger; // valid hysteresis range on passthrough low trigger limit
reg hyst_high_limit_pass_a; // valid hysteresis range on passthrough high trigger limit
reg hyst_low_limit_pass_a; // valid hysteresis range on passthrough low trigger limit
reg signed [DW:0] hyst_a_high_limit;
reg signed [DW:0] hyst_a_low_limit;
reg comp_high_b; // signal is over the limit
reg old_comp_high_b; // t + 1 version of comp_high_b
reg first_b_h_trigger; // valid hysteresis range on passthrough high trigger limit
reg first_b_l_trigger; // valid hysteresis range on passthrough low trigger limit
reg hyst_high_limit_pass_b; // valid hysteresis range on passthrough high trigger limit
reg hyst_low_limit_pass_b; // valid hysteresis range on passthrough low trigger limit
reg signed [DW:0] hyst_b_high_limit;
reg signed [DW:0] hyst_b_low_limit;
reg passthrough_high_a; // trigger when rising through the limit
reg passthrough_low_a; // trigger when fallingh thorugh the limit
reg passthrough_high_b; // trigger when rising through the limit
reg passthrough_low_b; // trigger when fallingh thorugh the limit
reg trigger_pin_a;
reg trigger_pin_b;
@ -422,22 +422,22 @@ module axi_adc_trigger #(
endcase
end
always @(posedge clk) begin
always @(*) begin
case(function_a)
2'h0: trigger_adc_a = comp_low_a_s;
2'h1: trigger_adc_a = comp_high_a;
2'h2: trigger_adc_a = passthrough_high_a_s;
2'h3: trigger_adc_a = passthrough_low_a_s;
2'h2: trigger_adc_a = passthrough_high_a;
2'h3: trigger_adc_a = passthrough_low_a;
default: trigger_adc_a = comp_low_a_s;
endcase
end
always @(posedge clk) begin
always @(*) begin
case(function_b)
2'h0: trigger_adc_b = comp_low_b_s;
2'h1: trigger_adc_b = comp_high_b;
2'h2: trigger_adc_b = passthrough_high_b_s;
2'h3: trigger_adc_b = passthrough_low_b_s;
2'h2: trigger_adc_b = passthrough_high_b;
2'h3: trigger_adc_b = passthrough_low_b;
default: trigger_adc_b = comp_low_b_s;
endcase
end
@ -483,55 +483,85 @@ module axi_adc_trigger #(
end
always @(posedge clk) begin
if (reset == 1'b1) begin
comp_high_a <= 1'b0;
old_comp_high_a <= 1'b0;
passthrough_high_a <= 1'b0;
passthrough_low_a <= 1'b0;
hyst_a_high_limit <= {DW{1'b0}};
hyst_a_low_limit <= {DW{1'b0}};
hyst_high_limit_pass_a <= 1'b0;
hyst_low_limit_pass_a <= 1'b0;
end else begin
if (data_valid_a == 1'b1) begin
hyst_a_high_limit <= limit_a_cmp + hysteresis_a[DW:0];
hyst_a_low_limit <= limit_a_cmp - hysteresis_a[DW:0];
if (data_a_cmp >= limit_a_cmp) begin
comp_high_a <= 1'b1;
first_a_h_trigger <= passthrough_high_a_s ? 0 : first_a_h_trigger;
if (data_a_cmp > hyst_a_high_limit) begin
first_a_l_trigger <= 1'b1;
end
end else begin
comp_high_a <= 1'b0;
first_a_l_trigger <= (passthrough_low_a_s) ? 0 : first_a_l_trigger;
end
if (data_a_cmp > hyst_a_high_limit) begin
hyst_low_limit_pass_a <= 1'b1;
end else begin
hyst_low_limit_pass_a <= (passthrough_low_a) ? 1'b0 : hyst_low_limit_pass_a;
end
if (data_a_cmp < hyst_a_low_limit) begin
first_a_h_trigger <= 1'b1;
end
hyst_high_limit_pass_a <= 1'b1;
end else begin
hyst_high_limit_pass_a <= passthrough_high_a ? 1'b0 : hyst_high_limit_pass_a;
end
old_comp_high_a <= comp_high_a;
passthrough_high_a <= !old_comp_high_a & comp_high_a & hyst_high_limit_pass_a;
passthrough_low_a <= old_comp_high_a & !comp_high_a & hyst_low_limit_pass_a;
end
end
end
assign passthrough_high_a_s = !old_comp_high_a & comp_high_a & first_a_h_trigger;
assign passthrough_low_a_s = old_comp_high_a & !comp_high_a & first_a_l_trigger;
assign comp_low_a_s = !comp_high_a;
always @(posedge clk) begin
if (reset == 1'b1) begin
comp_high_b <= 1'b0;
old_comp_high_b <= 1'b0;
passthrough_high_b <= 1'b0;
passthrough_low_b <= 1'b0;
hyst_b_high_limit <= {DW{1'b0}};
hyst_b_low_limit <= {DW{1'b0}};
hyst_high_limit_pass_b <= 1'b0;
hyst_low_limit_pass_b <= 1'b0;
end else begin
if (data_valid_b == 1'b1) begin
hyst_b_high_limit <= limit_b_cmp + hysteresis_b[DW:0];
hyst_b_low_limit <= limit_b_cmp - hysteresis_b[DW:0];
if (data_b_cmp >= limit_b_cmp) begin
comp_high_b <= 1'b1;
first_b_h_trigger <= (passthrough_high_b_s == 1) ? 0 : first_b_h_trigger;
if (data_b_cmp > hyst_b_high_limit) begin
first_b_l_trigger <= 1'b1;
end
end else begin
comp_high_b <= 1'b0;
first_b_l_trigger <= (passthrough_low_b_s == 1) ? 0 : first_b_l_trigger;
end
if (data_b_cmp > hyst_b_high_limit) begin
hyst_low_limit_pass_b <= 1'b1;
end else begin
hyst_low_limit_pass_b <= (passthrough_low_b) ? 1'b0 : hyst_low_limit_pass_b;
end
if (data_b_cmp < hyst_b_low_limit) begin
first_b_h_trigger <= 1'b1;
end
hyst_high_limit_pass_b <= 1'b1;
end else begin
hyst_high_limit_pass_b <= passthrough_high_b ? 1'b0 : hyst_high_limit_pass_b;
end
old_comp_high_b <= comp_high_b;
passthrough_high_b <= !old_comp_high_b & comp_high_b & hyst_high_limit_pass_b;
passthrough_low_b <= old_comp_high_b & !comp_high_b & hyst_low_limit_pass_b;
end
end
end
assign passthrough_high_b_s = !old_comp_high_b & comp_high_b & first_b_h_trigger;
assign passthrough_low_b_s = old_comp_high_b & !comp_high_b & first_b_l_trigger;
assign comp_low_b_s = !comp_high_b;
axi_adc_trigger_reg adc_trigger_registers (