From 6595c7c0284b8af78bedd0f9eee64e459167765b Mon Sep 17 00:00:00 2001
From: Eric Kooistra <kooistra@astron.nl>
Date: Thu, 14 Mar 2024 09:18:11 +0100
Subject: [PATCH] Use c_bsn_latency_first_node = 1 to reduce circular buffer
size.
---
.../libraries/sdp/src/vhdl/sdp_beamformer_remote.vhd | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/applications/lofar2/libraries/sdp/src/vhdl/sdp_beamformer_remote.vhd b/applications/lofar2/libraries/sdp/src/vhdl/sdp_beamformer_remote.vhd
index f6a29ba481..0029571356 100644
--- a/applications/lofar2/libraries/sdp/src/vhdl/sdp_beamformer_remote.vhd
+++ b/applications/lofar2/libraries/sdp/src/vhdl/sdp_beamformer_remote.vhd
@@ -71,8 +71,14 @@ architecture str of sdp_beamformer_remote is
constant c_fifo_size : natural := 2**ceil_log2((c_block_size * 9) / 16); -- 9/16 = 36/64, 1 block of
-- 64 bit words rounded to the next power of 2 = 1024.
- constant c_bsn_latency_max : natural := 2; -- max 2 blocks latency per node in chain
- constant c_bsn_latency_first_node : natural := 2;
+ -- Max 2 blocks latency per node in chain. Use c_bsn_latency_first_node = 1
+ -- for first node is possible, because it does not have to align with remote
+ -- input. By using c_bsn_latency_first_node = 1 the circular buffer size
+ -- becomes true_log_pow2(1 + g_nof_aligners_max * c_bsn_latency_max +
+ -- c_bsn_latency_first_node) = true_log_pow2(1 + (16 - 1) * 2 + 1) = 32
+ -- blocks, instead of true_log_pow2(1 + 16 * 2) = 64 blocks.
+ constant c_bsn_latency_max : natural := 2;
+ constant c_bsn_latency_first_node : natural := 1;
signal chain_node_index : natural range 0 to c_sdp_N_pn_max - 1 := 0;
--
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