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[rtl] make sure FIFO size is always a power of 2

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stnolting 2023-10-29 07:26:46 +01:00
parent fc43fba2a8
commit 774a0119ad
1 changed files with 13 additions and 16 deletions
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29
rtl/core/neorv32_fifo.vhd
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@ -65,13 +65,16 @@ end neorv32_fifo;
architecture neorv32_fifo_rtl of neorv32_fifo is
-- make sure FIFO depth is a power of two --
constant fifo_depth_c : natural := cond_sel_natural_f(is_power_of_two_f(FIFO_DEPTH), FIFO_DEPTH, 2**index_size_f(FIFO_DEPTH));
-- FIFO --
type fifo_data_t is array (0 to FIFO_DEPTH-1) of std_ulogic_vector(FIFO_WIDTH-1 downto 0);
type fifo_data_t is array (0 to fifo_depth_c-1) of std_ulogic_vector(FIFO_WIDTH-1 downto 0);
type fifo_t is record
we : std_ulogic; -- write enable
re : std_ulogic; -- read enable
w_pnt : std_ulogic_vector(index_size_f(FIFO_DEPTH) downto 0); -- write pointer
r_pnt : std_ulogic_vector(index_size_f(FIFO_DEPTH) downto 0); -- read pointer
w_pnt : std_ulogic_vector(index_size_f(fifo_depth_c) downto 0); -- write pointer
r_pnt : std_ulogic_vector(index_size_f(fifo_depth_c) downto 0); -- read pointer
data : fifo_data_t; -- fifo memory
buf : std_ulogic_vector(FIFO_WIDTH-1 downto 0); -- if single-entry FIFO
match : std_ulogic;
@ -84,16 +87,10 @@ architecture neorv32_fifo_rtl of neorv32_fifo is
signal fifo : fifo_t;
-- misc --
signal level_diff : std_ulogic_vector(index_size_f(FIFO_DEPTH) downto 0);
signal level_diff : std_ulogic_vector(index_size_f(fifo_depth_c) downto 0);
begin
-- Sanity Checks --------------------------------------------------------------------------
-- -------------------------------------------------------------------------------------------
assert not (FIFO_DEPTH = 0) report "NEORV32 CONFIG ERROR: FIFO depth has to be > 0." severity error;
assert not (is_power_of_two_f(FIFO_DEPTH) = false) report "NEORV32 CONFIG ERROR: FIFO depth has to be a power of two." severity error;
-- Access Control -------------------------------------------------------------------------
-- -------------------------------------------------------------------------------------------
fifo.re <= re_i when (FIFO_SAFE = false) else (re_i and fifo.avail); -- SAFE = read only if data available
@ -127,7 +124,7 @@ begin
-- FIFO Status ----------------------------------------------------------------------------
-- -------------------------------------------------------------------------------------------
check_large:
if (FIFO_DEPTH > 1) generate
if (fifo_depth_c > 1) generate
fifo.match <= '1' when (fifo.r_pnt(fifo.r_pnt'left-1 downto 0) = fifo.w_pnt(fifo.w_pnt'left-1 downto 0)) else '0';
fifo.full <= '1' when (fifo.r_pnt(fifo.r_pnt'left) /= fifo.w_pnt(fifo.w_pnt'left)) and (fifo.match = '1') else '0';
fifo.empty <= '1' when (fifo.r_pnt(fifo.r_pnt'left) = fifo.w_pnt(fifo.w_pnt'left)) and (fifo.match = '1') else '0';
@ -136,7 +133,7 @@ begin
end generate;
check_small:
if (FIFO_DEPTH = 1) generate
if (fifo_depth_c = 1) generate
fifo.match <= '1' when (fifo.r_pnt(0) = fifo.w_pnt(0)) else '0';
fifo.full <= not fifo.match;
fifo.empty <= fifo.match;
@ -176,7 +173,7 @@ begin
-- FIFO Memory - Write --------------------------------------------------------------------
-- -------------------------------------------------------------------------------------------
fifo_memory: -- real FIFO memory (several entries)
if (FIFO_DEPTH > 1) generate
if (fifo_depth_c > 1) generate
sync_read: process(clk_i)
begin
if rising_edge(clk_i) then
@ -189,7 +186,7 @@ begin
end generate;
fifo_buffer: -- simple register (single entry)
if (FIFO_DEPTH = 1) generate
if (fifo_depth_c = 1) generate
sync_read: process(clk_i)
begin
if rising_edge(clk_i) then
@ -208,7 +205,7 @@ begin
if (FIFO_RSYNC = false) generate
async_read: process(fifo)
begin
if (FIFO_DEPTH = 1) then
if (fifo_depth_c = 1) then
rdata_o <= fifo.buf;
else
rdata_o <= fifo.data(to_integer(unsigned(fifo.r_pnt(fifo.r_pnt'left-1 downto 0))));
@ -221,7 +218,7 @@ begin
async_read: process(clk_i)
begin
if rising_edge(clk_i) then
if (FIFO_DEPTH = 1) then
if (fifo_depth_c = 1) then
rdata_o <= fifo.buf;
else
rdata_o <= fifo.data(to_integer(unsigned(fifo.r_pnt(fifo.r_pnt'left-1 downto 0))));