| Line 12... |
Line 12... |
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-- Please read file /doc/ion_project.txt for usage instructions.
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-- Please read file /doc/ion_project.txt for usage instructions.
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--------------------------------------------------------------------------------
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--------------------------------------------------------------------------------
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--### MIPS-I things not implemented
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--### MIPS-I things not implemented
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--
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--
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-- 1.- RTE instruction (or ERET) missing, with CP0.SR KUo/IEo & KUP/IEp flags.
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-- 1.- Most of the R3000 CP0 registers and of course all of the CP1.
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-- 2.- Most of the R3000 CP0 registers and of course all of the CP1.
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-- 2.- External interrupts missing, with CP0.SR IR, NMI and IM7..0 flags.
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-- 3.- External interrupts missing, with CP0.SR IR, NMI and IM7..0 flags.
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--
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--
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--### Things with provisional implementation
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--### Things with provisional implementation
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--
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--
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-- 1.- Load interlocks: the pipeline is stalled for every load instruction, even
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-- 1.- Load interlocks: the pipeline is stalled for every load instruction, even
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-- if the target register is not used in the following instruction. So that
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-- if the target register is not used in the following instruction. So that
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| Line 34... |
Line 33... |
-- BUT there's no address checking and user code can still access kernel
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-- BUT there's no address checking and user code can still access kernel
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-- space in this version.
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-- space in this version.
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-- Besides, see point 2 above about the missing SR bits.
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-- Besides, see point 2 above about the missing SR bits.
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--
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--
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--------------------------------------------------------------------------------
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--------------------------------------------------------------------------------
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-- KNOWN BUGS:
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--
|
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-- 1.- The instruction after entering user mode (i.e. the instruction after the
|
|
-- MTC0 or RFE that clears the KU flag) is executed in kernel mode.
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-- This can be easily fixed but is not very urgent.
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--------------------------------------------------------------------------------
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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_arith.all;
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use ieee.std_logic_arith.all;
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use ieee.std_logic_unsigned.all;
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use ieee.std_logic_unsigned.all;
|
