| Line 80... |
Line 80... |
-- : preventing code from setting the I bit. When enabled, only
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-- : preventing code from setting the I bit. When enabled, only
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-- : interrupts can set the I bit, allowing for more robust memory
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-- : interrupts can set the I bit, allowing for more robust memory
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-- : protection by preventing errant code execution from
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-- : protection by preventing errant code execution from
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-- : inadvertently entering an interrupt state.
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-- : inadvertently entering an interrupt state.
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-- :
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-- :
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-- : Default_Int_Flag allows the initial state of the I bit to be
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-- : This setting also sets I bit at startup so that any
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-- : set at startup. If set, initialization code may be run in an
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-- : initialization code may be run in an ISR context, initially
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-- : ISR context, disabling memory protection initially. Init code
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-- : bypassing memory protection. Init code should clear the I bit
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-- : should clear the I bit when done;
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-- : when done;
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-- :
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-- :
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-- : Default_Interrupt_Mask sets the intial/reset value of the
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-- : Default_Interrupt_Mask sets the intial/reset value of the
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-- : interrupt mask. To remain true to the original core, which
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-- : interrupt mask. To remain true to the original core, which
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-- : had no interrupt mask, this should be set to x"FF". Otherwise
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-- : had no interrupt mask, this should be set to x"FF". Otherwise
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-- : it can be initialized to any value. Note that Enable_NMI
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-- : it can be initialized to any value. Note that Enable_NMI
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| Line 224... |
Line 224... |
-- start set so that initialization code can run,
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-- start set so that initialization code can run,
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-- but not be hijacked later to corrupt any memory
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-- but not be hijacked later to corrupt any memory
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-- write protection later.
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-- write protection later.
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-- Seth Henry 05/21/20 Supervisor_Mode now protects the interrupt mask
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-- Seth Henry 05/21/20 Supervisor_Mode now protects the interrupt mask
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-- and stack pointer as well.
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-- and stack pointer as well.
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-- Seth Henry 05/24/20 Removed the Default_Int_Flag, as it is covered by
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-- Supervisor_Mode. If Supervisor_Mode isn't set,
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-- code can simply use STP to set the bit
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library ieee;
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library ieee;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_unsigned.all;
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use ieee.std_logic_unsigned.all;
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use ieee.std_logic_arith.all;
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use ieee.std_logic_arith.all;
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| Line 247... |
Line 250... |
BRK_Implements_WAI : boolean := false; -- BRK -> Wait for Int
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BRK_Implements_WAI : boolean := false; -- BRK -> Wait for Int
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Enable_NMI : boolean := true; -- Force INTR0 enabled
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Enable_NMI : boolean := true; -- Force INTR0 enabled
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Sequential_Interrupts : boolean := false; -- Interruptable ISRs
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Sequential_Interrupts : boolean := false; -- Interruptable ISRs
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RTI_Ignores_GP_Flags : boolean := false; -- RTI sets all flags
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RTI_Ignores_GP_Flags : boolean := false; -- RTI sets all flags
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Supervisor_Mode : boolean := false; -- I bit is restricted
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Supervisor_Mode : boolean := false; -- I bit is restricted
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Default_Int_Flag : boolean := false; -- Start with I bit set
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Default_Interrupt_Mask : DATA_TYPE := x"FF"; -- Enable all Ints
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Default_Interrupt_Mask : DATA_TYPE := x"FF"; -- Enable all Ints
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Clock_Frequency : real -- Clock Frequency
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Clock_Frequency : real -- Clock Frequency
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);
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);
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port(
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port(
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Clock : in std_logic;
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Clock : in std_logic;
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| Line 1002... |
Line 1004... |
|
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for i in 0 to 7 loop
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for i in 0 to 7 loop
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Regfile(i) <= x"00";
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Regfile(i) <= x"00";
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end loop;
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end loop;
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Flags <= x"00";
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Flags <= x"00";
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if( Default_Int_Flag )then
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if( Supervisor_Mode )then
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Flags(PSR_I) <= '1';
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Flags(PSR_I) <= '1';
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end if;
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end if;
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|
|
Open8_Bus.GP_Flags <= (others => '0');
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Open8_Bus.GP_Flags <= (others => '0');
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|
|
