From d81b2cd17636aae11fb20763b58e389bc3712596 Mon Sep 17 00:00:00 2001
From: Eric Kooistra <kooistra@astron.nl>
Date: Thu, 6 Oct 2022 12:29:13 +0200
Subject: [PATCH] Register ref_sync to ease timing closure for ref_sync fanout
to (many) dp_bsn_monitor_v2 instances.
---
.../base/dp/src/vhdl/dp_bsn_monitor_v2.vhd | 20 ++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/libraries/base/dp/src/vhdl/dp_bsn_monitor_v2.vhd b/libraries/base/dp/src/vhdl/dp_bsn_monitor_v2.vhd
index 452e97f76a..b45e247c30 100644
--- a/libraries/base/dp/src/vhdl/dp_bsn_monitor_v2.vhd
+++ b/libraries/base/dp/src/vhdl/dp_bsn_monitor_v2.vhd
@@ -104,6 +104,7 @@ ARCHITECTURE rtl OF dp_bsn_monitor_v2 IS
SIGNAL nxt_valid : STD_LOGIC;
SIGNAL sop : STD_LOGIC;
SIGNAL nxt_sop : STD_LOGIC;
+ SIGNAL sync_reg : STD_LOGIC;
SIGNAL sync : STD_LOGIC;
SIGNAL nxt_sync : STD_LOGIC;
SIGNAL bsn : STD_LOGIC_VECTOR(c_bsn_w-1 DOWNTO 0);
@@ -162,20 +163,19 @@ BEGIN
nxt_mon_nof_sop <= nof_sop WHEN sync='1' ELSE i_mon_nof_sop;
nxt_mon_nof_err <= nof_err WHEN sync='1' ELSE i_mon_nof_err;
nxt_mon_nof_valid <= nof_valid WHEN sync='1' ELSE i_mon_nof_valid;
- nxt_mon_latency <= latency WHEN sync='1' ELSE i_mon_latency;
+ nxt_mon_latency <= latency WHEN sync_reg='1' ELSE i_mon_latency; -- use sync_reg due to ref_sync_reg
nof_sop <= cnt_sop;
nof_err <= cnt_err;
nof_valid <= cnt_valid;
latency <= cnt_latency;
- -- Register ref_sync to ease timing closure for ref_sync fanout to (many) dp_bsn_monitor_v2 instances
- -- TODO if needed:
- -- Registering ref_sync assumes ref_sunc occurs before in_sosi.sync. When ref_sync = in_sosi.sync,
- -- then also the impact of registering ref_sync with respect to in_sosi and in_siso needs to be
- -- verified.
- --ref_sync_reg <= ref_sync WHEN rising_edge(clk);
- ref_sync_reg <= ref_sync;
+ -- Register ref_sync to ease timing closure for ref_sync fanout to (many) dp_bsn_monitor_v2
+ -- instances. The ref_sync_reg is used to restart cnt_latency. Therefore the sync_reg
+ -- (instead of sync) is needed to capture latency (= cnt_latency) not too early, so capture
+ -- cnt_latency at or after the cnt_latency has restarted.
+ sync_reg <= sync WHEN rising_edge(clk);
+ ref_sync_reg <= ref_sync WHEN rising_edge(clk);
u_sync_timeout_cnt : ENTITY common_lib.common_counter
GENERIC MAP (
@@ -216,6 +216,7 @@ BEGIN
sop <= '0';
err <= '0';
sync <= '0';
+ sync_reg <= '0';
bsn <= (OTHERS=>'0');
-- output
mon_evt <= '0';
@@ -236,7 +237,8 @@ BEGIN
sop <= nxt_sop;
err <= nxt_err;
sync <= nxt_sync;
- bsn <= nxt_bsn;
+ sync_reg <= sync;
+ bsn <= nxt_bsn;
-- output
mon_evt <= nxt_mon_evt;
sync_timeout <= nxt_sync_timeout;
--
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