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redpitaya-puzzlefw
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Delay timetagger signal to match ADC trigger

This commit is contained in:
Joris van Rantwijk 2024-09-22 15:01:25 +02:00
parent 7c10b554dc
commit 5ceb5ad882
2 changed files with 21 additions and 9 deletions
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2
fpga/rtl/puzzlefw_pkg.vhd
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@ -94,7 +94,7 @@ package puzzlefw_pkg is
-- Firmware info word.
constant fw_api_version: natural := 1;
constant fw_version_major: natural := 0;
constant fw_version_minor: natural := 8;
constant fw_version_minor: natural := 9;
constant fw_info_word: std_logic_vector(31 downto 0) :=
x"4a"
& std_logic_vector(to_unsigned(fw_api_version, 8))

28
fpga/rtl/timetagger.vhd
View File

@ -64,7 +64,9 @@ architecture arch of timetagger is
overflow: std_logic;
marker_pending: std_logic;
marker_holdoff: std_logic;
cur_sample: std_logic_vector(3 downto 0);
prev_sample: std_logic_vector(3 downto 0);
detected_events: std_logic_vector(3 downto 0);
pending_events: std_logic_vector(3 downto 0);
fifo_in_valid: std_logic;
fifo_in_evmask: std_logic_vector(3 downto 0);
@ -76,7 +78,9 @@ architecture arch of timetagger is
overflow => '0',
marker_pending => '0',
marker_holdoff => '0',
cur_sample => (others => '0'),
prev_sample => (others => '0'),
detected_events => (others => '0'),
pending_events => (others => '0'),
fifo_in_valid => '0',
fifo_in_evmask => (others => '0'),
@ -184,20 +188,28 @@ begin
--
-- Detect events and write to FIFO.
---
--
-- This logic delays the digital input path in order to match the delay
-- in the analog acquisition chain. An event timestamp is assigned
-- after a delay of 3 clock cycles following a change in "dig_sample".
--
-- Hold previous input state.
v.prev_sample := dig_sample;
-- Capture input state.
v.cur_sample := dig_sample;
-- Keep previous input state.
v.prev_sample := r.cur_sample;
-- Detect events on enabled channels.
for i in 0 to 3 loop
v.fifo_in_evmask(i) :=
(channel_en(2*i) and (not r.prev_sample(i)) and dig_sample(i))
or (channel_en(2*i+1) and r.prev_sample(i) and (not dig_sample(i)));
v.detected_events(i) :=
(channel_en(2*i) and (not r.prev_sample(i)) and r.cur_sample(i))
or (channel_en(2*i+1) and r.prev_sample(i) and (not r.cur_sample(i)));
end loop;
-- Write changes to FIFO.
if (r.overflow = '0') and (or_reduce(v.fifo_in_evmask) = '1') then
-- Write detected events to FIFO.
v.fifo_in_evmask := r.detected_events;
if (r.overflow = '0') and (or_reduce(r.detected_events) = '1') then
v.fifo_in_valid := '1';
else
v.fifo_in_valid := '0';