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-- #################################################################################################
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-- #################################################################################################
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-- # << NEORV32 - Bus Keeper (BUSKEEPER) >> #
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-- # << NEORV32 - Bus Keeper (BUSKEEPER) >> #
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-- # ********************************************************************************************* #
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-- # ********************************************************************************************* #
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-- # This unit monitors the processor-internal bus. If the accesses INTERNAL (IMEM if enabled, #
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-- # This unit monitors the processor-internal bus. If the accessed INTERNAL (IMEM if enabled, #
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-- # DMEM if enabled, BOOTROM + IO region) module does not respond within the defined number of #
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-- # DMEM if enabled, BOOTROM + IO region) module does not respond within the defined number of #
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-- # cycles (VHDL package: max_proc_int_response_time_c) it asserts the error signal to inform the #
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-- # cycles (VHDL package: max_proc_int_response_time_c) the BUS KEEPER asserts the error signal #
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-- # CPU / bus driver. This timeout does not track accesses via the processor-external bus #
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-- # to inform the CPU / bus driver. #
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-- # interface! #
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-- # #
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-- # WARNING: The bus keeper timeout does not track accesses via the processor-external bus #
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-- # interface! If the timeout-function of the Wishbone interface is not used, the CPU #
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-- # might be permanently stalled by an an unacknowledged transfer! If the external bus #
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-- # interface is disabled, ALL accesses by the CPU are internal. #
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-- # ********************************************************************************************* #
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-- # ********************************************************************************************* #
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-- # BSD 3-Clause License #
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-- # BSD 3-Clause License #
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-- # #
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-- # #
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-- # Copyright (c) 2021, Stephan Nolting. All rights reserved. #
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-- # Copyright (c) 2021, Stephan Nolting. All rights reserved. #
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-- # #
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-- # #
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library neorv32;
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library neorv32;
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use neorv32.neorv32_package.all;
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use neorv32.neorv32_package.all;
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entity neorv32_bus_keeper is
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entity neorv32_bus_keeper is
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generic (
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generic (
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-- External memory interface --
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MEM_EXT_EN : boolean := false; -- implement external memory bus interface?
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-- Internal instruction memory --
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-- Internal instruction memory --
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MEM_INT_IMEM_EN : boolean := true; -- implement processor-internal instruction memory
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MEM_INT_IMEM_EN : boolean := true; -- implement processor-internal instruction memory
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MEM_INT_IMEM_SIZE : natural := 8*1024; -- size of processor-internal instruction memory in bytes
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MEM_INT_IMEM_SIZE : natural := 8*1024; -- size of processor-internal instruction memory in bytes
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-- Internal data memory --
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-- Internal data memory --
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MEM_INT_DMEM_EN : boolean := true; -- implement processor-internal data memory
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MEM_INT_DMEM_EN : boolean := true; -- implement processor-internal data memory
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elsif rising_edge(clk_i) then
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elsif rising_edge(clk_i) then
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-- pending access? --
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-- pending access? --
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control.bus_err <= '0';
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control.bus_err <= '0';
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if (control.pending = '0') then -- idle
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if (control.pending = '0') then -- idle
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if ((rden_i or wren_i) = '1') and (access_check.valid = '1') then
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if ((rden_i or wren_i) = '1') and ((access_check.valid = '1') or (MEM_EXT_EN = false)) then -- valid INTERNAL access
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control.pending <= '1';
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control.pending <= '1';
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end if;
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end if;
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else -- pending
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else -- pending
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if (ack_i = '1') or (err_i = '1') then -- termination by bus system
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if (ack_i = '1') or (err_i = '1') then -- termination by bus system
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control.pending <= '0';
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control.pending <= '0';
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