| Line 74... |
Line 74... |
-- : after an interrupt. By default, all of the flag bits are put
|
-- : after an interrupt. By default, all of the flag bits are put
|
-- : back to their original state. If this flag is set true, only
|
-- : back to their original state. If this flag is set true, only
|
-- : the lower four bits are restored, allowing ISR code to alter
|
-- : the lower four bits are restored, allowing ISR code to alter
|
-- : the GP flags persistently.
|
-- : the GP flags persistently.
|
-- :
|
-- :
|
|
-- : Supervisor_Mode, when set, disables the STP PSR_I instruction
|
|
-- : preventing code from setting the I bit. When enabled, only
|
|
-- : interrupts can set the I bit, allowing for more robust memory
|
|
-- : protection by preventing errant code execution from
|
|
-- : inadvertently entering an interrupt state.
|
|
-- :
|
|
-- : Default_Int_Flag allows the initial state of the I bit to be
|
|
-- : set at startup. If set, initialization code may be run in an
|
|
-- : ISR context, disabling memory protection initially. Init code
|
|
-- : should clear the I bit when done;
|
|
-- :
|
-- : Default_Interrupt_Mask sets the intial/reset value of the
|
-- : Default_Interrupt_Mask sets the intial/reset value of the
|
-- : interrupt mask. To remain true to the original core, which
|
-- : interrupt mask. To remain true to the original core, which
|
-- : had no interrupt mask, this should be set to x"FF". Otherwise
|
-- : had no interrupt mask, this should be set to x"FF". Otherwise
|
-- : it can be initialized to any value. Note that Enable_NMI
|
-- : it can be initialized to any value. Note that Enable_NMI
|
-- : will logically force the LSB high.
|
-- : will logically force the LSB high.
|
| Line 203... |
Line 214... |
-- Also added the I bit to the exported flags for
|
-- Also added the I bit to the exported flags for
|
-- use in memory protection schemes.
|
-- use in memory protection schemes.
|
-- Seth Henry 04/16/20 Modified to use new Open8 bus record. Also added
|
-- Seth Henry 04/16/20 Modified to use new Open8 bus record. Also added
|
-- reset and usec_tick logic to drive utility
|
-- reset and usec_tick logic to drive utility
|
-- signals. Also added Halt_Ack output.
|
-- signals. Also added Halt_Ack output.
|
|
-- Seth Henry 05/20/20 Added two new generics to alter the way the I bit
|
|
-- is handled. The Supervisor_Mode setting disables
|
|
-- STP PSR_I from being executed, preventing it
|
|
-- from being set outside of an ISR. The
|
|
-- Default_Int_Flag setting allows the I bit to
|
|
-- start set so that initialization code can run,
|
|
-- but not be hijacked later to corrupt any memory
|
|
-- write protection later.
|
|
|
library ieee;
|
library ieee;
|
use ieee.std_logic_1164.all;
|
use ieee.std_logic_1164.all;
|
use ieee.std_logic_unsigned.all;
|
use ieee.std_logic_unsigned.all;
|
use ieee.std_logic_arith.all;
|
use ieee.std_logic_arith.all;
|
| Line 225... |
Line 244... |
Enable_Auto_Increment : boolean := false; -- Modify indexed instr
|
Enable_Auto_Increment : boolean := false; -- Modify indexed instr
|
BRK_Implements_WAI : boolean := false; -- BRK -> Wait for Int
|
BRK_Implements_WAI : boolean := false; -- BRK -> Wait for Int
|
Enable_NMI : boolean := true; -- Force INTR0 enabled
|
Enable_NMI : boolean := true; -- Force INTR0 enabled
|
Sequential_Interrupts : boolean := false; -- Interruptable ISRs
|
Sequential_Interrupts : boolean := false; -- Interruptable ISRs
|
RTI_Ignores_GP_Flags : boolean := false; -- RTI sets all flags
|
RTI_Ignores_GP_Flags : boolean := false; -- RTI sets all flags
|
|
Supervisor_Mode : boolean := false; -- I bit is restricted
|
|
Default_Int_Flag : boolean := false; -- Start with I bit set
|
Default_Interrupt_Mask : DATA_TYPE := x"FF"; -- Enable all Ints
|
Default_Interrupt_Mask : DATA_TYPE := x"FF"; -- Enable all Ints
|
Clock_Frequency : real -- Clock Frequency
|
Clock_Frequency : real -- Clock Frequency
|
);
|
);
|
port(
|
port(
|
Clock : in std_logic;
|
Clock : in std_logic;
|
| Line 595... |
Line 616... |
Cache_Ctrl <= CACHE_PREFETCH;
|
Cache_Ctrl <= CACHE_PREFETCH;
|
PC_Ctrl.Offset <= PC_REV2;
|
PC_Ctrl.Offset <= PC_REV2;
|
DP_Ctrl.Src <= DATA_WR_REG;
|
DP_Ctrl.Src <= DATA_WR_REG;
|
DP_Ctrl.Reg <= ACCUM;
|
DP_Ctrl.Reg <= ACCUM;
|
|
|
|
when OP_STP =>
|
|
PC_Ctrl.Offset <= PC_NEXT;
|
|
if( Supervisor_Mode )then
|
|
if( SubOp /= PSR_I )then
|
|
ALU_Ctrl.Oper <= Opcode;
|
|
ALU_Ctrl.Reg <= SubOp;
|
|
end if;
|
|
else
|
|
ALU_Ctrl.Oper <= Opcode;
|
|
ALU_Ctrl.Reg <= SubOp;
|
|
end if;
|
|
|
when others =>
|
when others =>
|
PC_Ctrl.Offset <= PC_NEXT;
|
PC_Ctrl.Offset <= PC_NEXT;
|
ALU_Ctrl.Oper <= Opcode;
|
ALU_Ctrl.Oper <= Opcode;
|
ALU_Ctrl.Reg <= SubOp;
|
ALU_Ctrl.Reg <= SubOp;
|
|
|
| Line 965... |
Line 998... |
|
|
for i in 0 to 7 loop
|
for i in 0 to 7 loop
|
Regfile(i) <= x"00";
|
Regfile(i) <= x"00";
|
end loop;
|
end loop;
|
Flags <= x"00";
|
Flags <= x"00";
|
|
if( Default_Int_Flag )then
|
|
Flags(PSR_I) <= '1';
|
|
end if;
|
|
|
Open8_Bus.GP_Flags <= (others => '0');
|
Open8_Bus.GP_Flags <= (others => '0');
|
|
|
elsif( rising_edge(Clock) )then
|
elsif( rising_edge(Clock) )then
|
|
|
