URL
https://opencores.org/ocsvn/neorv32/neorv32/trunk
Subversion Repositories neorv32
[/] [neorv32/] [trunk/] [rtl/] [core/] [neorv32_bus_keeper.vhd] - Rev 65
Go to most recent revision | Compare with Previous | Blame | View Log
-- ################################################################################################# -- # << NEORV32 - Bus Keeper (BUSKEEPER) >> # -- # ********************************************************************************************* # -- # This unit monitors the processor-internal bus. If the accessed INTERNAL (IMEM if enabled, # -- # DMEM if enabled, BOOTROM + IO region) module does not respond within the defined number of # -- # cycles (VHDL package: max_proc_int_response_time_c) the BUS KEEPER asserts the error signal # -- # to inform the CPU / bus driver. # -- # # -- # WARNING: The bus keeper timeout does not track accesses via the processor-external bus # -- # interface! If the timeout-function of the Wishbone interface is not used, the CPU # -- # might be permanently stalled by an an unacknowledged transfer! If the external bus # -- # interface is disabled, ALL accesses by the CPU are internal. # -- # ********************************************************************************************* # -- # BSD 3-Clause License # -- # # -- # Copyright (c) 2021, Stephan Nolting. All rights reserved. # -- # # -- # Redistribution and use in source and binary forms, with or without modification, are # -- # permitted provided that the following conditions are met: # -- # # -- # 1. Redistributions of source code must retain the above copyright notice, this list of # -- # conditions and the following disclaimer. # -- # # -- # 2. Redistributions in binary form must reproduce the above copyright notice, this list of # -- # conditions and the following disclaimer in the documentation and/or other materials # -- # provided with the distribution. # -- # # -- # 3. Neither the name of the copyright holder nor the names of its contributors may be used to # -- # endorse or promote products derived from this software without specific prior written # -- # permission. # -- # # -- # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS # -- # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF # -- # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE # -- # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, # -- # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE # -- # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED # -- # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING # -- # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED # -- # OF THE POSSIBILITY OF SUCH DAMAGE. # -- # ********************************************************************************************* # -- # The NEORV32 Processor - https://github.com/stnolting/neorv32 (c) Stephan Nolting # -- ################################################################################################# library ieee; use ieee.std_logic_1164.all; use ieee.numeric_std.all; library neorv32; use neorv32.neorv32_package.all; entity neorv32_bus_keeper is generic ( -- External memory interface -- MEM_EXT_EN : boolean; -- implement external memory bus interface? -- Internal instruction memory -- MEM_INT_IMEM_EN : boolean; -- implement processor-internal instruction memory MEM_INT_IMEM_SIZE : natural; -- size of processor-internal instruction memory in bytes -- Internal data memory -- MEM_INT_DMEM_EN : boolean; -- implement processor-internal data memory MEM_INT_DMEM_SIZE : natural -- size of processor-internal data memory in bytes ); port ( -- host access -- clk_i : in std_ulogic; -- global clock line rstn_i : in std_ulogic; -- global reset line, low-active addr_i : in std_ulogic_vector(31 downto 0); -- address rden_i : in std_ulogic; -- read enable wren_i : in std_ulogic; -- write enable ack_i : in std_ulogic; -- transfer acknowledge from bus system err_i : in std_ulogic; -- transfer error from bus system err_o : out std_ulogic -- bus error ); end neorv32_bus_keeper; architecture neorv32_bus_keeper_rtl of neorv32_bus_keeper is -- access check -- type access_check_t is record int_imem : std_ulogic; int_dmem : std_ulogic; int_bootrom_io : std_ulogic; valid : std_ulogic; end record; signal access_check : access_check_t; -- controller -- type control_t is record pending : std_ulogic; timeout : std_ulogic_vector(index_size_f(max_proc_int_response_time_c)-1 downto 0); bus_err : std_ulogic; end record; signal control : control_t; begin -- Sanity Check -------------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- 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; -- Access Control ------------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- -- access to processor-internal IMEM or DMEM? -- access_check.int_imem <= '1' when (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'; access_check.int_dmem <= '1' when (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'; -- access to processor-internal BOOTROM or IO devices? -- access_check.int_bootrom_io <= '1' when (addr_i(31 downto 16) = boot_rom_base_c(31 downto 16)) else '0'; -- hacky! -- actual internal bus access? -- access_check.valid <= access_check.int_imem or access_check.int_dmem or access_check.int_bootrom_io; -- Keeper --------------------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- keeper_control: process(rstn_i, clk_i) begin if (rstn_i = '0') then control.pending <= '0'; control.bus_err <= '0'; control.timeout <= (others => def_rst_val_c); elsif rising_edge(clk_i) then -- pending access? -- control.bus_err <= '0'; if (control.pending = '0') then -- idle if ((rden_i or wren_i) = '1') and ((access_check.valid = '1') or (MEM_EXT_EN = false)) then -- valid INTERNAL access control.pending <= '1'; end if; else -- pending if (ack_i = '1') or (err_i = '1') then -- termination by bus system control.pending <= '0'; elsif (or_reduce_f(control.timeout) = '0') then -- timeout! terminate bus transfer control.pending <= '0'; control.bus_err <= '1'; end if; end if; -- timeout counter -- if (control.pending = '0') then control.timeout <= std_ulogic_vector(to_unsigned(max_proc_int_response_time_c, index_size_f(max_proc_int_response_time_c))); else control.timeout <= std_ulogic_vector(unsigned(control.timeout) - 1); -- countdown timer end if; end if; end process keeper_control; err_o <= control.bus_err; end neorv32_bus_keeper_rtl;
Go to most recent revision | Compare with Previous | Blame | View Log