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Platform-independent core collection
Commit e0ecab7f authored by Dimitris Lampridis's avatar Dimitris Lampridis
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inferred_sync_fifo: fix full flag for g_show_ahead. 

Previously, the full flag was asserted at g_size-1 when using g_show_ahead.
The new implementation solves this. However, for backward compatibility,
the default is to still use the previous behaviour. Set g_show_ahead_legacy_mode
to false to switch to the new one.
parent e854ab00
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Showing with 54 additions and 4 deletions
modules/genrams/common/inferred_sync_fifo.vhd
View file @ e0ecab7f
......@@ -12,7 +12,7 @@
-- - configurable full/empty/almost full/almost empty/word count signals
--
--------------------------------------------------------------------------------
-- Copyright CERN 2011-2018
-- Copyright CERN 2011-2020
--------------------------------------------------------------------------------
-- Copyright and related rights are licensed under the Solderpad Hardware
-- License, Version 2.0 (the "License"); you may not use this file except
......@@ -38,6 +38,12 @@ entity inferred_sync_fifo is
g_size : natural;
g_show_ahead : boolean := false;
-- Previously, the full flag was asserted at g_size-1 when using g_show_ahead.
-- The new implementation solves this. However, for backward compatibility,
-- the default is to still use the previous behaviour. Set this to false to
-- switch to the new one.
g_show_ahead_legacy_mode : boolean := true;
-- Read-side flag selection
g_with_empty : boolean := true; -- with empty flag
g_with_full : boolean := true; -- with full flag
......@@ -84,6 +90,12 @@ architecture syn of inferred_sync_fifo is
begin -- syn
legacy_mode_check: assert g_show_ahead = false or g_show_ahead_legacy_mode = false
report legacy_mode_check'instance_name & ": show-ahead enabled for sync FIFO in " &
"legacy mode. In this mode, the full flag is asserted at g_SIZE-1. if you want the " &
"full flag to be asserted at g_SIZE, then disable g_SHOW_AHEAD_LEGACY_MODE."
severity NOTE;
we_int <= we_i and not full;
rd_int <= rd_i and not empty;
......@@ -135,7 +147,8 @@ begin -- syn
end if;
end process;
gen_comb_flags_showahead : if(g_show_ahead = true) generate
gen_comb_flags_showahead_legacy : if g_show_ahead = true and
g_show_ahead_legacy_mode = true generate
process(clk_i)
begin
......@@ -149,6 +162,34 @@ begin -- syn
end process;
full <= '1' when (wr_ptr + 1 = rd_ptr) else '0';
end generate gen_comb_flags_showahead_legacy;
gen_comb_flags_showahead : if g_show_ahead = true and
g_show_ahead_legacy_mode = false generate
process(clk_i)
begin
if rising_edge(clk_i) then
if rst_n_i = '0' then
guard_bit <= '0';
empty <= '1';
else
if wr_ptr = rd_ptr_muxed and guard_bit = '0' then
empty <= '1';
else
empty <= '0';
end if;
if(wr_ptr + 1 = rd_ptr and we_int = '1') then
guard_bit <= '1';
elsif(rd_i = '1') then
guard_bit <= '0';
end if;
end if;
end if;
end process;
full <= '1' when (wr_ptr = rd_ptr and guard_bit = '1') else '0';
end generate gen_comb_flags_showahead;
gen_comb_flags : if(g_register_flag_outputs = false and g_show_ahead = false) generate
......
modules/genrams/generic/generic_sync_fifo.vhd
View file @ e0ecab7f
......@@ -12,7 +12,7 @@
-- - configurable full/empty/almost full/almost empty/word count signals
--
--------------------------------------------------------------------------------
-- Copyright CERN 2011-2018
-- Copyright CERN 2011-2020
--------------------------------------------------------------------------------
-- Copyright and related rights are licensed under the Solderpad Hardware
-- License, Version 2.0 (the "License"); you may not use this file except
......@@ -38,7 +38,13 @@ entity generic_sync_fifo is
g_size : natural;
g_show_ahead : boolean := false;
-- Read-side flag selection
-- Previously, the full flag was asserted at g_size-1 when using g_show_ahead.
-- The new implementation solves this. However, for backward compatibility,
-- the default is to still use the previous behaviour. Set this to false to
-- switch to the new one.
g_show_ahead_legacy_mode : boolean := true;
-- Read-side flag selection
g_with_empty : boolean := true; -- with empty flag
g_with_full : boolean := true; -- with full flag
g_with_almost_empty : boolean := false;
......@@ -76,6 +82,7 @@ architecture syn of generic_sync_fifo is
g_data_width : natural;
g_size : natural;
g_show_ahead : boolean;
g_show_ahead_legacy_mode : boolean;
g_with_empty : boolean;
g_with_full : boolean;
g_with_almost_empty : boolean;
......@@ -105,6 +112,7 @@ begin -- syn
g_data_width => g_data_width,
g_size => g_size,
g_show_ahead => g_show_ahead,
g_show_ahead_legacy_mode => g_show_ahead_legacy_mode,
g_with_empty => g_with_empty,
g_with_full => g_with_full,
g_with_almost_empty => g_with_almost_empty,
......
modules/genrams/genram_pkg.vhd
View file @ e0ecab7f
......@@ -209,6 +209,7 @@ package genram_pkg is
g_data_width : natural;
g_size : natural;
g_show_ahead : boolean := false;
g_show_ahead_legacy_mode : boolean := true;
g_with_empty : boolean := true;
g_with_full : boolean := true;
g_with_almost_empty : boolean := false;
......
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