1 |
57 |
zero_gravi |
-- #################################################################################################
|
2 |
|
|
-- # << NEORV32 - Bus Keeper (BUSKEEPER) >> #
|
3 |
|
|
-- # ********************************************************************************************* #
|
4 |
59 |
zero_gravi |
-- # This unit monitors the processor-internal bus. If the accessed INTERNAL (IMEM if enabled, #
|
5 |
57 |
zero_gravi |
-- # DMEM if enabled, BOOTROM + IO region) module does not respond within the defined number of #
|
6 |
59 |
zero_gravi |
-- # cycles (VHDL package: max_proc_int_response_time_c) the BUS KEEPER asserts the error signal #
|
7 |
|
|
-- # to inform the CPU / bus driver. #
|
8 |
|
|
-- # #
|
9 |
|
|
-- # WARNING: The bus keeper timeout does not track accesses via the processor-external bus #
|
10 |
|
|
-- # interface! If the timeout-function of the Wishbone interface is not used, the CPU #
|
11 |
|
|
-- # might be permanently stalled by an an unacknowledged transfer! If the external bus #
|
12 |
|
|
-- # interface is disabled, ALL accesses by the CPU are internal. #
|
13 |
57 |
zero_gravi |
-- # ********************************************************************************************* #
|
14 |
|
|
-- # BSD 3-Clause License #
|
15 |
|
|
-- # #
|
16 |
|
|
-- # Copyright (c) 2021, Stephan Nolting. All rights reserved. #
|
17 |
|
|
-- # #
|
18 |
|
|
-- # Redistribution and use in source and binary forms, with or without modification, are #
|
19 |
|
|
-- # permitted provided that the following conditions are met: #
|
20 |
|
|
-- # #
|
21 |
|
|
-- # 1. Redistributions of source code must retain the above copyright notice, this list of #
|
22 |
|
|
-- # conditions and the following disclaimer. #
|
23 |
|
|
-- # #
|
24 |
|
|
-- # 2. Redistributions in binary form must reproduce the above copyright notice, this list of #
|
25 |
|
|
-- # conditions and the following disclaimer in the documentation and/or other materials #
|
26 |
|
|
-- # provided with the distribution. #
|
27 |
|
|
-- # #
|
28 |
|
|
-- # 3. Neither the name of the copyright holder nor the names of its contributors may be used to #
|
29 |
|
|
-- # endorse or promote products derived from this software without specific prior written #
|
30 |
|
|
-- # permission. #
|
31 |
|
|
-- # #
|
32 |
|
|
-- # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS #
|
33 |
|
|
-- # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF #
|
34 |
|
|
-- # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE #
|
35 |
|
|
-- # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, #
|
36 |
|
|
-- # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE #
|
37 |
|
|
-- # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED #
|
38 |
|
|
-- # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING #
|
39 |
|
|
-- # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED #
|
40 |
|
|
-- # OF THE POSSIBILITY OF SUCH DAMAGE. #
|
41 |
|
|
-- # ********************************************************************************************* #
|
42 |
|
|
-- # The NEORV32 Processor - https://github.com/stnolting/neorv32 (c) Stephan Nolting #
|
43 |
|
|
-- #################################################################################################
|
44 |
|
|
|
45 |
|
|
library ieee;
|
46 |
|
|
use ieee.std_logic_1164.all;
|
47 |
|
|
use ieee.numeric_std.all;
|
48 |
|
|
|
49 |
|
|
library neorv32;
|
50 |
|
|
use neorv32.neorv32_package.all;
|
51 |
|
|
|
52 |
|
|
entity neorv32_bus_keeper is
|
53 |
|
|
generic (
|
54 |
59 |
zero_gravi |
-- External memory interface --
|
55 |
62 |
zero_gravi |
MEM_EXT_EN : boolean; -- implement external memory bus interface?
|
56 |
57 |
zero_gravi |
-- Internal instruction memory --
|
57 |
62 |
zero_gravi |
MEM_INT_IMEM_EN : boolean; -- implement processor-internal instruction memory
|
58 |
|
|
MEM_INT_IMEM_SIZE : natural; -- size of processor-internal instruction memory in bytes
|
59 |
57 |
zero_gravi |
-- Internal data memory --
|
60 |
62 |
zero_gravi |
MEM_INT_DMEM_EN : boolean; -- implement processor-internal data memory
|
61 |
|
|
MEM_INT_DMEM_SIZE : natural -- size of processor-internal data memory in bytes
|
62 |
57 |
zero_gravi |
);
|
63 |
|
|
port (
|
64 |
|
|
-- host access --
|
65 |
66 |
zero_gravi |
clk_i : in std_ulogic; -- global clock line
|
66 |
|
|
rstn_i : in std_ulogic; -- global reset, low-active, async
|
67 |
|
|
addr_i : in std_ulogic_vector(31 downto 0); -- address
|
68 |
|
|
rden_i : in std_ulogic; -- read enable
|
69 |
|
|
wren_i : in std_ulogic; -- write enable
|
70 |
|
|
data_o : out std_ulogic_vector(31 downto 0); -- data out
|
71 |
|
|
ack_o : out std_ulogic; -- transfer acknowledge
|
72 |
|
|
err_o : out std_ulogic; -- transfer error
|
73 |
|
|
-- bus monitoring --
|
74 |
|
|
bus_addr_i : in std_ulogic_vector(31 downto 0); -- address
|
75 |
|
|
bus_rden_i : in std_ulogic; -- read enable
|
76 |
|
|
bus_wren_i : in std_ulogic; -- write enable
|
77 |
|
|
bus_ack_i : in std_ulogic; -- transfer acknowledge from bus system
|
78 |
|
|
bus_err_i : in std_ulogic -- transfer error from bus system
|
79 |
57 |
zero_gravi |
);
|
80 |
|
|
end neorv32_bus_keeper;
|
81 |
|
|
|
82 |
|
|
architecture neorv32_bus_keeper_rtl of neorv32_bus_keeper is
|
83 |
|
|
|
84 |
66 |
zero_gravi |
-- IO space: module base address --
|
85 |
|
|
constant hi_abb_c : natural := index_size_f(io_size_c)-1; -- high address boundary bit
|
86 |
|
|
constant lo_abb_c : natural := index_size_f(buskeeper_size_c); -- low address boundary bit
|
87 |
|
|
|
88 |
|
|
-- Control register --
|
89 |
|
|
constant ctrl_err_type_c : natural := 0; -- r/-: error type: 0=device error, 1=access timeout
|
90 |
|
|
constant ctrl_err_src_c : natural := 1; -- r/-: error source: 0=processor-external, 1=processor-internal
|
91 |
|
|
constant ctrl_err_flag_c : natural := 31; -- r/c: bus error encountered, sticky; cleared by writing zero
|
92 |
|
|
|
93 |
|
|
-- sticky error flag --
|
94 |
|
|
signal err_flag : std_ulogic;
|
95 |
|
|
|
96 |
|
|
-- access control --
|
97 |
|
|
signal acc_en : std_ulogic; -- module access enable
|
98 |
|
|
signal wren : std_ulogic; -- word write enable
|
99 |
|
|
signal rden : std_ulogic; -- read enable
|
100 |
|
|
|
101 |
|
|
-- bus access check --
|
102 |
57 |
zero_gravi |
type access_check_t is record
|
103 |
|
|
int_imem : std_ulogic;
|
104 |
|
|
int_dmem : std_ulogic;
|
105 |
|
|
int_bootrom_io : std_ulogic;
|
106 |
|
|
valid : std_ulogic;
|
107 |
|
|
end record;
|
108 |
|
|
signal access_check : access_check_t;
|
109 |
|
|
|
110 |
|
|
-- controller --
|
111 |
|
|
type control_t is record
|
112 |
66 |
zero_gravi |
pending : std_ulogic;
|
113 |
|
|
timeout : std_ulogic_vector(index_size_f(max_proc_int_response_time_c)-1 downto 0);
|
114 |
|
|
err_type : std_ulogic;
|
115 |
|
|
int_ext : std_ulogic;
|
116 |
|
|
bus_err : std_ulogic;
|
117 |
57 |
zero_gravi |
end record;
|
118 |
|
|
signal control : control_t;
|
119 |
|
|
|
120 |
|
|
begin
|
121 |
|
|
|
122 |
|
|
-- Sanity Check --------------------------------------------------------------------------
|
123 |
|
|
-- -------------------------------------------------------------------------------------------
|
124 |
|
|
assert not (max_proc_int_response_time_c < 2) report "NEORV32 PROCESSOR CONFIG ERROR! Processor-internal bus timeout <max_proc_int_response_time_c> has to >= 2." severity error;
|
125 |
|
|
|
126 |
|
|
|
127 |
|
|
-- Access Control -------------------------------------------------------------------------
|
128 |
|
|
-- -------------------------------------------------------------------------------------------
|
129 |
66 |
zero_gravi |
acc_en <= '1' when (addr_i(hi_abb_c downto lo_abb_c) = buskeeper_base_c(hi_abb_c downto lo_abb_c)) else '0';
|
130 |
|
|
wren <= acc_en and wren_i;
|
131 |
|
|
rden <= acc_en and rden_i;
|
132 |
|
|
|
133 |
|
|
|
134 |
|
|
-- Bus Access Check -----------------------------------------------------------------------
|
135 |
|
|
-- -------------------------------------------------------------------------------------------
|
136 |
57 |
zero_gravi |
-- access to processor-internal IMEM or DMEM? --
|
137 |
66 |
zero_gravi |
access_check.int_imem <= '1' when (bus_addr_i(31 downto index_size_f(MEM_INT_IMEM_SIZE)) = imem_base_c(31 downto index_size_f(MEM_INT_IMEM_SIZE))) and (MEM_INT_IMEM_EN = true) else '0';
|
138 |
|
|
access_check.int_dmem <= '1' when (bus_addr_i(31 downto index_size_f(MEM_INT_DMEM_SIZE)) = dmem_base_c(31 downto index_size_f(MEM_INT_DMEM_SIZE))) and (MEM_INT_DMEM_EN = true) else '0';
|
139 |
57 |
zero_gravi |
-- access to processor-internal BOOTROM or IO devices? --
|
140 |
66 |
zero_gravi |
access_check.int_bootrom_io <= '1' when (bus_addr_i(31 downto 16) = boot_rom_base_c(31 downto 16)) else '0'; -- hacky!
|
141 |
57 |
zero_gravi |
-- actual internal bus access? --
|
142 |
|
|
access_check.valid <= access_check.int_imem or access_check.int_dmem or access_check.int_bootrom_io;
|
143 |
|
|
|
144 |
|
|
|
145 |
66 |
zero_gravi |
-- Read/Write Access ----------------------------------------------------------------------
|
146 |
|
|
-- -------------------------------------------------------------------------------------------
|
147 |
|
|
rw_access: process(clk_i)
|
148 |
|
|
begin
|
149 |
|
|
if rising_edge(clk_i) then
|
150 |
|
|
-- bus handshake --
|
151 |
|
|
ack_o <= wren or rden;
|
152 |
|
|
|
153 |
|
|
-- read access --
|
154 |
|
|
data_o <= (others => '0');
|
155 |
|
|
if (rden = '1') then
|
156 |
|
|
data_o(ctrl_err_type_c) <= control.err_type;
|
157 |
|
|
data_o(ctrl_err_src_c) <= control.int_ext;
|
158 |
|
|
data_o(ctrl_err_flag_c) <= err_flag;
|
159 |
|
|
end if;
|
160 |
|
|
--
|
161 |
|
|
if (control.bus_err = '1') then
|
162 |
|
|
err_flag <= '1'; -- sticky error flag
|
163 |
|
|
elsif (rden = '1') then -- clear on read
|
164 |
|
|
err_flag <= '0';
|
165 |
|
|
end if;
|
166 |
|
|
end if;
|
167 |
|
|
end process rw_access;
|
168 |
|
|
|
169 |
|
|
|
170 |
57 |
zero_gravi |
-- Keeper ---------------------------------------------------------------------------------
|
171 |
|
|
-- -------------------------------------------------------------------------------------------
|
172 |
|
|
keeper_control: process(rstn_i, clk_i)
|
173 |
|
|
begin
|
174 |
|
|
if (rstn_i = '0') then
|
175 |
66 |
zero_gravi |
control.pending <= '0';
|
176 |
|
|
control.bus_err <= '0';
|
177 |
|
|
control.err_type <= def_rst_val_c;
|
178 |
|
|
control.int_ext <= def_rst_val_c;
|
179 |
|
|
control.timeout <= (others => def_rst_val_c);
|
180 |
|
|
err_o <= '0';
|
181 |
|
|
elsif rising_edge(clk_i) then
|
182 |
|
|
-- defaults --
|
183 |
57 |
zero_gravi |
control.bus_err <= '0';
|
184 |
|
|
|
185 |
66 |
zero_gravi |
-- access monitor: IDLE --
|
186 |
|
|
if (control.pending = '0') then
|
187 |
|
|
control.timeout <= std_ulogic_vector(to_unsigned(max_proc_int_response_time_c, index_size_f(max_proc_int_response_time_c)));
|
188 |
|
|
if (bus_rden_i = '1') or (bus_wren_i = '1') then
|
189 |
|
|
if (access_check.valid = '1') or (MEM_EXT_EN = false) then
|
190 |
|
|
control.int_ext <= '1'; -- processor-internal access
|
191 |
|
|
else
|
192 |
|
|
control.int_ext <= '0'; -- processor-external access
|
193 |
|
|
end if;
|
194 |
57 |
zero_gravi |
control.pending <= '1';
|
195 |
|
|
end if;
|
196 |
|
|
|
197 |
66 |
zero_gravi |
-- access monitor: PENDING --
|
198 |
57 |
zero_gravi |
else
|
199 |
|
|
control.timeout <= std_ulogic_vector(unsigned(control.timeout) - 1); -- countdown timer
|
200 |
66 |
zero_gravi |
if (bus_ack_i = '1') then -- normal termination by bus system
|
201 |
|
|
control.err_type <= '0'; -- don't care
|
202 |
|
|
control.bus_err <= '0';
|
203 |
|
|
control.pending <= '0';
|
204 |
|
|
elsif (bus_err_i = '1') then -- error termination by bus system
|
205 |
|
|
control.err_type <= '0'; -- device error
|
206 |
|
|
control.bus_err <= '1';
|
207 |
|
|
control.pending <= '0';
|
208 |
|
|
elsif (or_reduce_f(control.timeout) = '0') and (control.int_ext = '1') then -- timeout! terminate bus transfer (internal accesses only!)
|
209 |
|
|
control.err_type <= '1'; -- timeout error
|
210 |
|
|
control.bus_err <= '1';
|
211 |
|
|
control.pending <= '0';
|
212 |
|
|
end if;
|
213 |
57 |
zero_gravi |
end if;
|
214 |
66 |
zero_gravi |
|
215 |
|
|
-- only output timeout errors here - device errors are already propagated by the bus system --
|
216 |
|
|
err_o <= control.bus_err and control.err_type;
|
217 |
57 |
zero_gravi |
end if;
|
218 |
|
|
end process keeper_control;
|
219 |
|
|
|
220 |
|
|
|
221 |
|
|
end neorv32_bus_keeper_rtl;
|