diff --git a/libraries/base/dp/src/vhdl/dp_bsn_sync_scheduler.vhd b/libraries/base/dp/src/vhdl/dp_bsn_sync_scheduler.vhd
index 64242905331882b1fa4f1aa503c986be8acbe48d..9c888558625dbd66a51de1eb75c8cb7ca028d70b 100644
--- a/libraries/base/dp/src/vhdl/dp_bsn_sync_scheduler.vhd
+++ b/libraries/base/dp/src/vhdl/dp_bsn_sync_scheduler.vhd
@@ -1,24 +1,21 @@
--------------------------------------------------------------------------------
---
--- Copyright (C) 2012
+-- --------------------------------------------------------------------------
+-- Copyright 2021
-- ASTRON (Netherlands Institute for Radio Astronomy) <http://www.astron.nl/>
-- P.O.Box 2, 7990 AA Dwingeloo, The Netherlands
--
--- This program is free software: you can redistribute it and/or modify
--- it under the terms of the GNU General Public License as published by
--- the Free Software Foundation, either version 3 of the License, or
--- (at your option) any later version.
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
--
--- This program is distributed in the hope that it will be useful,
--- but WITHOUT ANY WARRANTY; without even the implied warranty of
--- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
--- GNU General Public License for more details.
+-- http://www.apache.org/licenses/LICENSE-2.0
--
--- You should have received a copy of the GNU General Public License
--- along with this program. If not, see <http://www.gnu.org/licenses/>.
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+-- --------------------------------------------------------------------------
--
--------------------------------------------------------------------------------
-
-- Author: Eric Kooistra, 30 July 2021
-- Purpose :
-- Create programmable sync interval for input stream.
@@ -43,26 +40,39 @@
-- output is disable after an in_sosi.eop when ctrl_enable = '0'. If the
-- output is diabled, then the sosai control fields are forced to '0', the
-- other sosi fields of the in_sosi are passed on to the out_sosi.
--- * mon_input_current_bsn:
--- The user can read mon_input_current_bsn to determine a suitable
+-- * mon_current_input_bsn:
+-- The user can read mon_current_input_bsn to determine a suitable
-- ctrl_start_bsn in the future.
-- * mon_input_bsn_at_sync:
--- The user can read mon_input_current_bsn to determine a suitable
+-- The user can read mon_current_input_bsn to determine a suitable
-- ctrl_start_bsn in the future to create a output sync interval that is
-- aligned with the in_sosi.sync.
-- * mon_output_enable:
-- The user can read mon_output_enable to check whether the output is indeed
--- enabled or not.
+-- enabled or not (mon_output_enable = out_enable).
-- * mon_output_sync_bsn:
-- The sync interval calculation is robust to lost in_sosi blocks. As soon
-- as it receives a new in_sosi block it will try to determine the next
-- output_sync_bsn, even if blocks were lost for multiple output sync
--- intervals. If mon_output_sync_bsn - mon_input_current_bsn < 0 then the
+-- intervals. If mon_output_sync_bsn - mon_current_input_bsn < 0 then the
-- output sync interval calculation should catch up after some in_sosi
--- blocks. If mon_output_sync_bsn - mon_input_current_bsn > nof_blk then
+-- blocks. If mon_output_sync_bsn - mon_current_input_bsn > nof_blk then
-- something went wrong and then it may be necessary to recover using
--- ctrl_enable. If mon_output_sync_bsn - mon_input_current_bsn < nof_blk and
+-- ctrl_enable. If mon_output_sync_bsn - mon_current_input_bsn < nof_blk and
-- > 0 then that yields the number of blocks until the next output sync.
+-- * out_start:
+-- Pulse at out_sosi.sync with out_sosi.bsn = ctrl_start_bsn. The first
+-- out_sosi.sync interval will have nof_blk_max blocks.
+-- * out_enable:
+-- Goes high at first out_sosi.sync. In case of a restart when ctrl_enable
+-- was already '1', then the out_enable will go low and high to ensure that
+-- the restart out_sosi.sync interval will have nof_blk_max blocks. When
+-- ctrl_enable goes low or in case of a restart then out_enable will go
+-- low after an out_sosi.eop, to preserve complete out_sosi blocks. The
+-- out_enable is monitored via mon_output_enable, so that the user can
+-- check via MM whether an ctrl_enable access was applied. Typically the
+-- out_enable OUT can be left OPEN in an VHDL application, and only used for
+-- verification purposes in the test bench (tb).
-- For example:
-- . sample period Ts = 5 ns
-- . g_block_size = 1024 samples
@@ -114,7 +124,7 @@ ENTITY dp_bsn_sync_scheduler IS
ctrl_enable_evt : IN STD_LOGIC;
ctrl_interval_size : IN NATURAL;
ctrl_start_bsn : IN STD_LOGIC_VECTOR(g_bsn_w-1 DOWNTO 0) := (OTHERS=>'0');
- mon_input_current_bsn : OUT STD_LOGIC_VECTOR(g_bsn_w-1 DOWNTO 0);
+ mon_current_input_bsn : OUT STD_LOGIC_VECTOR(g_bsn_w-1 DOWNTO 0);
mon_input_bsn_at_sync : OUT STD_LOGIC_VECTOR(g_bsn_w-1 DOWNTO 0);
mon_output_enable : OUT STD_LOGIC;
mon_output_sync_bsn : OUT STD_LOGIC_VECTOR(g_bsn_w-1 DOWNTO 0);
@@ -122,8 +132,8 @@ ENTITY dp_bsn_sync_scheduler IS
-- Streaming
in_sosi : IN t_dp_sosi;
out_sosi : OUT t_dp_sosi;
- out_start : OUT STD_LOGIC;
- out_enable : OUT STD_LOGIC
+ out_start : OUT STD_LOGIC; -- pulse at out_sosi.sync at ctrl_start_bsn
+ out_enable : OUT STD_LOGIC -- for tb verification purposes
);
END dp_bsn_sync_scheduler;
@@ -163,7 +173,7 @@ BEGIN
ASSERT g_block_size >= 2 REPORT "g_block_size must be >= 2." SEVERITY FAILURE;
-- Capture monitoring info
- mon_input_current_bsn <= in_sosi.bsn(g_bsn_w-1 DOWNTO 0) WHEN rising_edge(clk) AND in_sosi.sop = '1';
+ mon_current_input_bsn <= in_sosi.bsn(g_bsn_w-1 DOWNTO 0) WHEN rising_edge(clk) AND in_sosi.sop = '1';
mon_input_bsn_at_sync <= in_sosi.bsn(g_bsn_w-1 DOWNTO 0) WHEN rising_edge(clk) AND in_sosi.sync = '1';
mon_output_enable <= r.output_enable;
mon_output_sync_bsn <= r.output_sync_bsn;
@@ -191,6 +201,8 @@ BEGIN
END IF;
-- Initialization: calculate number of blocks per output sync interval
+ -- . use r.enable_init instead of v.enable_init to easy timing closure and
+ -- because functionally it makes no difference.
IF r.enable_init = '1' THEN
-- Assume ctrl_start_bsn is scheduled more than nof_blk block clk cycles
-- after the ctrl_enable_evt, so there is sufficient time until
@@ -229,16 +241,21 @@ BEGIN
-- Enable / disable control
IF ctrl_enable = '0' THEN
- v.enable := '0'; -- disable when ctrl_enable requests disable
+ -- Disable output when ctrl_enable requests disable.
+ v.enable := '0';
ELSIF ctrl_enable_evt = '1' THEN
- v.enable := '0'; -- disable when ctrl_enable requests re-enable
+ -- ctrl_enable is on, so this is a re-enable. First disable output.
+ v.enable := '0';
ELSIF r.enable_init = '0' THEN
- IF r.hold_eop = '1' THEN
- -- enable after in_sosi.eop, so that r.enable has caused
- -- v.output_enable = '0', to ensure that a re-enable starts
- -- with the nof_blk_max sync interval. Otherwise
- -- v.output_enable = '1' can cause that re-enable can restart
- -- with the nof_blk_min sync interval
+ -- ctrl_enable is still on, so now enable the output. In case of an
+ -- enable, then the output was already disabled. In case of a re-enable,
+ -- then wait until the output got disabled.
+ -- Enabling the output from disabled state ensures that the output will
+ -- start or restart with nof_blk_max in the first sync interval.
+ -- Otherwise with re-enabling from enabled state, it is undefined
+ -- whether the first sync interval after the restart will have
+ -- nof_blk_min or nof_blk_max blocks.
+ IF r.output_enable = '0' THEN
v.enable := '1';
END IF;
END IF;
@@ -252,7 +269,7 @@ BEGIN
v.hold_eop := '1';
END IF;
- IF r.enable = '1' THEN
+ IF v.enable = '1' THEN
-- Output enable at in_sosi.sop start_bsn
IF in_sosi.sop = '1' THEN
IF UNSIGNED(in_sosi.bsn) = UNSIGNED(r.start_bsn) THEN
@@ -304,7 +321,7 @@ BEGIN
-- Assume output_sync_bsn is in future
v.update_bsn := '0';
- -- else last r.input_bsn will be used to keep update_bsn active for
+ -- else: last r.input_bsn will be used to keep update_bsn active for
-- more clk cycles to catch up for lost input blocks.
END IF;
@@ -313,11 +330,15 @@ BEGIN
v.input_bsn := in_sosi.bsn(g_bsn_w-1 DOWNTO 0);
END IF;
- -- Catch up with output_sync_bsn in case of lost input blocks
+ -- Catch up with output_sync_bsn in case of lost input blocks. If many
+ -- input blocks were lost (e.g. > nof_blk_max), then catching up the
+ -- output_sync_bsn to the current input_bsn can cause that one or more
+ -- output_sync will not be made active, but that is acceptable in case
+ -- recovery from of lost input blocks.
IF v.output_enable = '1' THEN
IF UNSIGNED(r.input_bsn) > UNSIGNED(v.output_sync_bsn) THEN
-- Missed one or more input blocks, fast forward to look for next
- -- output_sync_bsn
+ -- output_sync_bsn in every clk cycle.
v.update_bsn := '1';
END IF;
END IF;