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Commit f29b0683 authored by Wesley W. Terpstra's avatar Wesley W. Terpstra
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usb: improve timings 

The datasheet is wrong for tXFLG on read and write
  => use 80ns instead of 70ns
Also use a single register input for fd_i
  => makes fast register input mode possible for the pins
parent e35c293d
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hdl/eb_usb_core/ez_usb_fifos.vhd
+ 23
− 19
View file @ f29b0683
......@@ -33,9 +33,7 @@ entity ez_usb_fifos is
g_board_delay : integer := 2; -- path length from FPGA to chip
g_margin : integer := 4; -- too lazy to consider FPGA timing constraints? increase this.
g_fifo_width : integer := 8; -- # of FIFO data pins connected (8 or 16)
g_num_fifos : integer := 4 -- always 4 for FX2LP (EP2, EP4, EP6, EP8)
);
g_num_fifos : integer := 4); -- always 4 for FX2LP (EP2, EP4, EP6, EP8)
port(
clk_sys_i : in std_logic;
rstn_i : in std_logic;
......@@ -61,8 +59,8 @@ end ez_usb_fifos;
architecture rtl of ez_usb_fifos is
-- Timing constants from EZ-USB data sheet
constant c_tXFLG_a : integer := 11; -- FIFOADR to FLAGS output propagation delay
constant c_tXFLG_r : integer := 70; -- SLRD to FLAGS output propagation delay
constant c_tXFLG_w : integer := 70; -- SLWR to FLAGS output propagation delay
constant c_tXFLG_r : integer := 70+10; -- SLRD to FLAGS output propagation delay (+10 b/c datasheet lies!)
constant c_tXFLG_w : integer := 70+10; -- SLWR to FLAGS output propagation delay
constant c_tXFLG_e : integer := 115; -- PKTEND to FLAGS output propagation delay
constant c_tSFA : integer := 10; -- FIFOADR to SLRD/SLWR/PKTEND setup time (adr -> falling edge)
constant c_tFAH : integer := 10; -- RD/WR/PKTEND to FIFOADR hold time (rising edge -> adr)
......@@ -101,22 +99,25 @@ architecture rtl of ez_usb_fifos is
constant c_latch_flags : integer := 2; -- >= 2 to synchronize async signal
constant c_dispatch : integer := 1;
constant c_set_addr : integer := f_cycles(f_max(c_tXFLG_a + g_board_delay*2,
c_tSFA - f_ns(c_latch_flags+c_dispatch)));
c_tSFA - f_ns(c_latch_flags+c_dispatch)));
constant c_drive_read : integer := f_cycles(f_max(c_tOEon, c_tXFD) + g_board_delay*2);
constant c_latch_data : integer := f_cycles(c_tRDpwl - f_ns(c_drive_read));
constant c_idle_read : integer := f_cycles(f_max(c_tRDpwh - f_ns(c_latch_flags+c_dispatch),
f_max(c_tXFLG_r - f_ns(c_drive_read+c_latch_data),
f_max(c_tOEoff - f_ns(c_latch_data),
c_tFAH))));
constant c_idle_read : integer := f_cycles(f_max(c_tRDpwh - f_ns(c_latch_flags+c_dispatch),
f_max(c_tXFLG_r + g_board_delay*2
- f_ns(c_drive_read+c_latch_data),
f_max(c_tOEoff - f_ns(c_latch_data+c_latch_flags+c_dispatch),
c_tFAH - f_ns(c_latch_flags+c_dispatch)))));
constant c_drive_write : integer := f_cycles(f_max(c_tWRpwl, c_tSFD));
constant c_idle_write : integer := f_cycles(c_tFDH);
constant c_idle_data : integer := f_cycles(f_max(c_tWRpwh - f_ns(c_latch_flags+c_dispatch+c_idle_write),
f_max(c_tXFLG_w - f_ns(c_drive_write+c_idle_write),
c_tFAH - f_ns(c_idle_write))));
f_max(c_tXFLG_w + g_board_delay*2
- f_ns(c_drive_write+c_idle_write),
c_tFAH - f_ns(c_idle_write+c_latch_flags+c_dispatch))));
constant c_drive_pktend : integer := f_cycles(c_tPEpwl);
constant c_idle_pktend : integer := f_cycles(f_max(c_tPEpwh - f_ns(c_latch_flags+c_dispatch),
f_max(c_tXFLG_e - f_ns(c_drive_pktend),
c_tFAH)));
f_max(c_tXFLG_e + g_board_delay*2
- f_ns(c_drive_pktend),
c_tFAH - f_ns(c_latch_flags+c_dispatch))));
constant c_max_count : integer :=
f_max(c_latch_flags, f_max(c_dispatch, f_max(c_set_addr, f_max(c_drive_read,
......@@ -132,6 +133,7 @@ architecture rtl of ez_usb_fifos is
signal notfull : std_logic_vector(c_latch_flags-1 downto 0) := (others => '0');
signal count : unsigned(f_ceil_log2(c_max_count)-1 downto 0) := (others => '0');
signal addr : unsigned(f_ceil_log2(g_num_fifos)-1 downto 0) := (others => '0');
signal fd_r : word := (others => '0');
signal dat4usb : words(g_num_fifos-1 downto 0) := (others => (others => '0'));
signal dat4wb : words(g_num_fifos-1 downto 0) := (others => (others => '0'));
signal needend : std_logic_vector(g_num_fifos-1 downto 0) := (others => '0');
......@@ -163,6 +165,7 @@ begin
notfull <= (others => '0');
count <= (others => '0');
addr <= (others => '0');
fd_r <= (others => '0');
dat4usb <= (others => (others => '0'));
dat4wb <= (others => (others => '0'));
needend <= (others => '0');
......@@ -183,6 +186,8 @@ begin
case state is
when LATCH_FLAGS =>
ack(to_integer(addr)) <= '0';
notfull <= flagbn_i & notfull(notfull'left downto 1);
notempty <= flagcn_i & notempty(notempty'left downto 1);
......@@ -258,7 +263,7 @@ begin
sloen_o <= '1';
if count = 0 then
dat4wb(to_integer(addr)) <= fd_i;
fd_r <= fd_i;
end if;
if count /= c_latch_data-1 then
......@@ -266,18 +271,18 @@ begin
else
state <= IDLE_READ;
count <= (others => '0');
ack(to_integer(addr)) <= '1';
end if;
when IDLE_READ =>
dat4wb(to_integer(addr)) <= fd_r;
slrdn_o <= '1';
ack(to_integer(addr)) <= '0';
if count /= c_idle_read-1 then
count <= count + 1;
else
state <= LATCH_FLAGS;
count <= (others => '0');
ack(to_integer(addr)) <= '1';
end if;
when DRIVE_WRITE =>
......@@ -291,12 +296,10 @@ begin
else
state <= IDLE_WRITE;
count <= (others => '0');
ack(to_integer(addr)) <= '1';
end if;
when IDLE_WRITE =>
slwrn_o <= '1';
ack(to_integer(addr)) <= '0';
if count /= c_idle_write-1 then
count <= count + 1;
......@@ -313,6 +316,7 @@ begin
else
state <= LATCH_FLAGS;
count <= (others => '0');
ack(to_integer(addr)) <= '1';
end if;
when DRIVE_PKTEND =>
......
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