A tiny Open POWER ISA softcore written in VHDL 2008
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298 lines
9.2 KiB

library ieee;
use ieee.std_logic_1164.all;
use ieee.math_real.all;
library work;
use work.wishbone_types.all;
entity dmi_dtm is
generic(ABITS : INTEGER:=8;
DBITS : INTEGER:=64);
port(sys_clk : in std_ulogic;
sys_reset : in std_ulogic;
dmi_addr : out std_ulogic_vector(ABITS - 1 downto 0);
dmi_din : in std_ulogic_vector(DBITS - 1 downto 0);
dmi_dout : out std_ulogic_vector(DBITS - 1 downto 0);
dmi_req : out std_ulogic;
dmi_wr : out std_ulogic;
dmi_ack : in std_ulogic
-- dmi_err : in std_ulogic TODO: Add error response
);
end entity dmi_dtm;
architecture behaviour of dmi_dtm is
-- Signals coming out of the JTAGG block
signal jtag_reset_n : std_ulogic;
signal tdi : std_ulogic;
signal tdo : std_ulogic;
signal tck : std_ulogic;
signal jce1 : std_ulogic;
signal jshift : std_ulogic;
signal update : std_ulogic;
-- signals to match dmi_dtb_xilinx
signal jtag_reset : std_ulogic;
signal capture : std_ulogic;
signal jtag_clk : std_ulogic;
signal sel : std_ulogic;
signal shift : std_ulogic;
-- delays
signal jce1_d : std_ulogic;
constant TCK_DELAY : INTEGER := 8;
signal tck_d : std_ulogic_vector(TCK_DELAY+1 downto 1);
-- ** JTAG clock domain **
-- Shift register
signal shiftr : std_ulogic_vector(ABITS + DBITS + 1 downto 0);
-- Latched request
signal request : std_ulogic_vector(ABITS + DBITS + 1 downto 0);
-- A request is present
signal jtag_req : std_ulogic;
-- Synchronizer for jtag_rsp (sys clk -> jtag_clk)
signal dmi_ack_0 : std_ulogic;
signal dmi_ack_1 : std_ulogic;
-- ** sys clock domain **
-- Synchronizer for jtag_req (jtag clk -> sys clk)
signal jtag_req_0 : std_ulogic;
signal jtag_req_1 : std_ulogic;
-- ** combination signals
signal jtag_bsy : std_ulogic;
signal op_valid : std_ulogic;
signal rsp_op : std_ulogic_vector(1 downto 0);
-- ** Constants **
constant DMI_REQ_NOP : std_ulogic_vector(1 downto 0) := "00";
constant DMI_REQ_RD : std_ulogic_vector(1 downto 0) := "01";
constant DMI_REQ_WR : std_ulogic_vector(1 downto 0) := "10";
constant DMI_RSP_OK : std_ulogic_vector(1 downto 0) := "00";
constant DMI_RSP_BSY : std_ulogic_vector(1 downto 0) := "11";
attribute ASYNC_REG : string;
attribute ASYNC_REG of jtag_req_0: signal is "TRUE";
attribute ASYNC_REG of jtag_req_1: signal is "TRUE";
attribute ASYNC_REG of dmi_ack_0: signal is "TRUE";
attribute ASYNC_REG of dmi_ack_1: signal is "TRUE";
-- ECP5 JTAGG
component JTAGG is
generic (
ER1 : string := "ENABLED";
ER2 : string := "ENABLED"
);
port(
JTDO1 : in std_ulogic;
JTDO2 : in std_ulogic;
JTDI : out std_ulogic;
JTCK : out std_ulogic;
JRTI1 : out std_ulogic;
JRTI2 : out std_ulogic;
JSHIFT : out std_ulogic;
JUPDATE : out std_ulogic;
JRSTN : out std_ulogic;
JCE1 : out std_ulogic;
JCE2 : out std_ulogic
);
end component;
component LUT4 is
generic (
INIT : std_logic_vector
);
port(
A : in STD_ULOGIC;
B : in STD_ULOGIC;
C : in STD_ULOGIC;
D : in STD_ULOGIC;
Z : out STD_ULOGIC
);
end component;
begin
jtag: JTAGG
generic map(
ER2 => "DISABLED"
)
port map (
JTDO1 => tdo,
JTDO2 => '0',
JTDI => tdi,
JTCK => tck,
JRTI1 => open,
JRTI2 => open,
JSHIFT => jshift,
JUPDATE => update,
JRSTN => jtag_reset_n,
JCE1 => jce1,
JCE2 => open
);
-- JRTI1 looks like it could be connected to SEL, but
-- in practise JRTI1 is only high briefly, not for the duration
-- of the transmission. possibly mw_debug could be modified.
-- The ecp5 is probably the only jtag device anyway.
sel <= '1';
-- TDI needs to align with TCK, we use LUT delays here.
-- From https://github.com/enjoy-digital/litex/pull/1087
tck_d(1) <= tck;
del: for i in 1 to TCK_DELAY generate
attribute keep : boolean;
attribute keep of l: label is true;
begin
l: LUT4
generic map(
INIT => b"0000_0000_0000_0010"
)
port map (
A => tck_d(i),
B => '0', C => '0', D => '0',
Z => tck_d(i+1)
);
end generate;
jtag_clk <= tck_d(TCK_DELAY+1);
-- capture signal
jce1_sync : process(jtag_clk)
begin
if rising_edge(jtag_clk) then
jce1_d <= jce1;
capture <= jce1 and not jce1_d;
end if;
end process;
-- latch the shift signal, otherwise
-- we miss the last shift in
-- (maybe because we are delaying tck?)
shift_sync : process(jtag_clk)
begin
if (sys_reset = '1') then
shift <= '0';
elsif rising_edge(jtag_clk) then
shift <= jshift;
end if;
end process;
jtag_reset <= not jtag_reset_n;
-- dmi_req synchronization
dmi_req_sync : process(sys_clk)
begin
-- sys_reset is synchronous
if rising_edge(sys_clk) then
if (sys_reset = '1') then
jtag_req_0 <= '0';
jtag_req_1 <= '0';
else
jtag_req_0 <= jtag_req;
jtag_req_1 <= jtag_req_0;
end if;
end if;
end process;
dmi_req <= jtag_req_1;
-- dmi_ack synchronization
dmi_ack_sync: process(jtag_clk, jtag_reset)
begin
-- jtag_reset is async (see comments)
if jtag_reset = '1' then
dmi_ack_0 <= '0';
dmi_ack_1 <= '0';
elsif rising_edge(jtag_clk) then
dmi_ack_0 <= dmi_ack;
dmi_ack_1 <= dmi_ack_0;
end if;
end process;
-- jtag_bsy indicates whether we can start a new request, we can when
-- we aren't already processing one (jtag_req) and the synchronized ack
-- of the previous one is 0.
--
jtag_bsy <= jtag_req or dmi_ack_1;
-- decode request type in shift register
with shiftr(1 downto 0) select op_valid <=
'1' when DMI_REQ_RD,
'1' when DMI_REQ_WR,
'0' when others;
-- encode response op
rsp_op <= DMI_RSP_BSY when jtag_bsy = '1' else DMI_RSP_OK;
-- Some DMI out signals are directly driven from the request register
dmi_addr <= request(ABITS + DBITS + 1 downto DBITS + 2);
dmi_dout <= request(DBITS + 1 downto 2);
dmi_wr <= '1' when request(1 downto 0) = DMI_REQ_WR else '0';
-- TDO is wired to shift register bit 0
tdo <= shiftr(0);
-- Main state machine. Handles shift registers, request latch and
-- jtag_req latch. Could be split into 3 processes but it's probably
-- not worthwhile.
--
shifter: process(jtag_clk, jtag_reset, sys_reset)
begin
if jtag_reset = '1' or sys_reset = '1' then
shiftr <= (others => '0');
jtag_req <= '0';
request <= (others => '0');
elsif rising_edge(jtag_clk) then
-- Handle jtag "commands" when sel is 1
if sel = '1' then
-- Shift state, rotate the register
if shift = '1' then
shiftr <= tdi & shiftr(ABITS + DBITS + 1 downto 1);
end if;
-- Update state (trigger)
--
-- Latch the request if we aren't already processing one and
-- it has a valid command opcode.
--
if update = '1' and op_valid = '1' then
if jtag_bsy = '0' then
request <= shiftr;
jtag_req <= '1';
end if;
-- Set the shift register "op" to "busy". This will prevent
-- us from re-starting the command on the next update if
-- the command completes before that.
shiftr(1 downto 0) <= DMI_RSP_BSY;
end if;
-- Request completion.
--
-- Capture the response data for reads and clear request flag.
--
-- Note: We clear req (and thus dmi_req) here which relies on tck
-- ticking and sel set. This means we are stuck with dmi_req up if
-- the jtag interface stops. Slaves must be resilient to this.
--
if jtag_req = '1' and dmi_ack_1 = '1' then
jtag_req <= '0';
if request(1 downto 0) = DMI_REQ_RD then
request(DBITS + 1 downto 2) <= dmi_din;
end if;
end if;
-- Capture state, grab latch content with updated status
if capture = '1' then
shiftr <= request(ABITS + DBITS + 1 downto 2) & rsp_op;
end if;
end if;
end if;
end process;
end architecture behaviour;