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-- #################################################################################################
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-- #################################################################################################
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-- # << NEORV32 - Bus Interface Unit >> #
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-- # << NEORV32 - Bus Interface Unit >> #
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-- # ********************************************************************************************* #
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-- # ********************************************************************************************* #
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-- # Instruction and data bus interfaces. #
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-- # Instruction and data bus interfaces and physical memory protection (PMP). #
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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) 2020, Stephan Nolting. All rights reserved. #
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-- # Copyright (c) 2020, Stephan Nolting. All rights reserved. #
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-- # #
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-- # #
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CPU_EXTENSION_RISCV_C : boolean := true; -- implement compressed extension?
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CPU_EXTENSION_RISCV_C : boolean := true; -- implement compressed extension?
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BUS_TIMEOUT : natural := 15; -- cycles after which a valid bus access will timeout
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BUS_TIMEOUT : natural := 15; -- cycles after which a valid bus access will timeout
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-- Physical memory protection (PMP) --
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-- Physical memory protection (PMP) --
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PMP_USE : boolean := false; -- implement physical memory protection?
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PMP_USE : boolean := false; -- implement physical memory protection?
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PMP_NUM_REGIONS : natural := 4; -- number of regions (1..4)
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PMP_NUM_REGIONS : natural := 4; -- number of regions (1..4)
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PMP_GRANULARITY : natural := 16 -- granularity (0=none, 1=8B, 2=16B, 3=32B, ...)
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PMP_GRANULARITY : natural := 16 -- granularity (1=8B, 2=16B, 3=32B, ...)
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);
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);
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port (
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port (
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-- global control --
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-- global control --
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clk_i : in std_ulogic; -- global clock, rising edge
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clk_i : in std_ulogic; -- global clock, rising edge
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rstn_i : in std_ulogic; -- global reset, low-active, async
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rstn_i : in std_ulogic; -- global reset, low-active, async
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-- check access type and regions's permissions --
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-- check access type and regions's permissions --
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pmp_check_permission: process(pmp, pmp_ctrl_i, priv_mode_i)
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pmp_check_permission: process(pmp, pmp_ctrl_i, priv_mode_i)
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begin
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begin
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for r in 0 to PMP_NUM_REGIONS-1 loop -- iterate over all regions
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for r in 0 to PMP_NUM_REGIONS-1 loop -- iterate over all regions
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if ((priv_mode_i = u_priv_mode_c) or (pmp_ctrl_i(r)(pmp_cfg_l_c) = '1')) and -- user privilege level or locked pmp entry - enforce permissions also for machine mode
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if ((priv_mode_i = u_priv_mode_c) or (pmp_ctrl_i(r)(pmp_cfg_l_c) = '1')) and -- user privilege level or locked pmp entry -> enforce permissions also for machine mode
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(pmp_ctrl_i(r)(pmp_cfg_ah_c downto pmp_cfg_al_c) /= pmp_off_mode_c) then -- active entry
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(pmp_ctrl_i(r)(pmp_cfg_ah_c downto pmp_cfg_al_c) /= pmp_off_mode_c) then -- active entry
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pmp.if_fault(r) <= pmp.i_match(r) and (not pmp_ctrl_i(r)(pmp_cfg_x_c)); -- fetch access match no execute permission
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pmp.if_fault(r) <= pmp.i_match(r) and (not pmp_ctrl_i(r)(pmp_cfg_x_c)); -- fetch access match no execute permission
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pmp.ld_fault(r) <= pmp.d_match(r) and (not pmp_ctrl_i(r)(pmp_cfg_r_c)); -- load access match no read permission
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pmp.ld_fault(r) <= pmp.d_match(r) and (not pmp_ctrl_i(r)(pmp_cfg_r_c)); -- load access match no read permission
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pmp.st_fault(r) <= pmp.d_match(r) and (not pmp_ctrl_i(r)(pmp_cfg_w_c)); -- store access match no write permission
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pmp.st_fault(r) <= pmp.d_match(r) and (not pmp_ctrl_i(r)(pmp_cfg_w_c)); -- store access match no write permission
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else
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else
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