129 lines
3.3 KiB
ArmAsm
129 lines
3.3 KiB
ArmAsm
; This file is part of stage0.
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;
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; stage0 is free software: you can redistribute it and/or modify
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; it under the terms of the GNU General Public License as published by
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; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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;
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; stage0 is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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;
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; You should have received a copy of the GNU General Public License
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; along with stage0. If not, see <http://www.gnu.org/licenses/>.
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:start
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LOADUI R10 0x0F ; Byte mask
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LOADUI R11 1 ; Our toggle
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LOADUI R13 0x600 ; Where we are starting our Stack
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;; R14 is storing our condition code
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;; R15 is storing our nybble
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;; Prep TAPE_01
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LOADUI R0 0x1100
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FOPEN_READ
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;; Prep TAPE_02
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LOADUI R0 0x1101
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FOPEN_WRITE
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;; Main program loop
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;; Halts when done
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:loop
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LOADUI R1 0x1100 ; Read from tape_01
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FGETC ; Read a Char
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;; Check for EOF
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CMPI R14 R0 0
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JUMP.GE R14 @.L1
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CALLI R13 @finish
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:.L1
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LOADUI R1 0 ; Write to Char to TTY
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FPUTC ; Print the Char
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CALLI R13 @hex ; Convert it
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CMPI R14 R0 0 ; Check if it is hex
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JUMP.L R14 @loop ; Don't use nonhex chars
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JUMP.Z R11 @.L99 ; Jump if toggled
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;; Process first byte of pair
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AND R15 R0 R10 ; Store First nibble
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FALSE R11 ; Flip the toggle
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JUMP @loop
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:.L99
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SL0I R15 4 ; Shift our first nibble
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AND R0 R0 R10 ; Mask out top
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ADD R0 R0 R15 ; Combine nibbles
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LOADI R11 1 ; Flip the toggle
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LOADUI R1 0x1101 ; Write the combined byte
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FPUTC ; To TAPE_02
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JUMP @loop ; Try to get more bytes
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;; Hex function
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;; Converts Ascii chars to their hex values
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;; Or -1 if not a hex char
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;; Returns to whatever called it
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:hex
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;; Deal with line comments starting with #
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CMPUI R14 R0 35
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JUMP.E R14 @ascii_comment
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;; Deal with line comments starting with ;
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CMPUI R14 R0 59
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JUMP.E R14 @ascii_comment
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;; Deal with all ascii less than '0'
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CMPUI R14 R0 48
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JUMP.L R14 @ascii_other
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;; Deal with '0'-'9'
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CMPUI R14 R0 57
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JUMP.LE R14 @ascii_num
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;; Deal with all ascii less than 'A'
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CMPUI R14 R0 65
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JUMP.L R14 @ascii_other
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;; Deal with 'A'-'F'
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CMPUI R14 R0 70
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JUMP.LE R14 @ascii_high
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;; Deal with all ascii less than 'a'
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CMPUI R14 R0 97
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JUMP.L R14 @ascii_other
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;; Deal with 'a'-'f'
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CMPUI R14 R0 102
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JUMP.LE R14 @ascii_low
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;; Ignore the rest
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JUMP @ascii_other
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:ascii_num
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SUBUI R0 R0 48
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RET R13
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:ascii_low
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SUBUI R0 R0 87
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RET R13
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:ascii_high
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SUBUI R0 R0 55
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RET R13
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:ascii_other
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TRUE R0
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RET R13
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:ascii_comment
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LOADUI R1 0x1100 ; Read from TAPE_01
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FGETC ; Read another char
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CMPUI R14 R0 10 ; Stop at the end of line
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LOADUI R1 0 ; Write to TTY
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FPUTC ; The char we just read
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JUMP.NE R14 @ascii_comment ; Otherwise keep looping
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JUMP @ascii_other
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;; Finish function
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;; Cleans up at the end of the program
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;; Performs the HALT
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:finish
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LOADUI R0 0x1100 ; Close TAPE_01
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FCLOSE
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LOADUI R0 0x1101 ; Close TAPE_02
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FCLOSE
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HALT
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