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; #################################################################################################
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; # < crt0.asm - general neo430 application start-up code > #
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; # ********************************************************************************************* #
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; # BSD 3-Clause License #
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; # #
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; # Copyright (c) 2020, Stephan Nolting. All rights reserved. #
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; # #
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; # Redistribution and use in source and binary forms, with or without modification, are #
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; # permitted provided that the following conditions are met: #
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; # #
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; # 1. Redistributions of source code must retain the above copyright notice, this list of #
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; # conditions and the following disclaimer. #
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; # #
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; # 2. Redistributions in binary form must reproduce the above copyright notice, this list of #
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; # conditions and the following disclaimer in the documentation and/or other materials #
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; # provided with the distribution. #
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; # #
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; # 3. Neither the name of the copyright holder nor the names of its contributors may be used to #
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; # endorse or promote products derived from this software without specific prior written #
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; # permission. #
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; # #
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; # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS #
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; # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF #
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; # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE #
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; # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, #
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; # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE #
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; # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED #
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; # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING #
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; # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED #
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; # OF THE POSSIBILITY OF SUCH DAMAGE. #
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; # ********************************************************************************************* #
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; # The NEO430 Processor - https://github.com/stnolting/neo430 #
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; #################################################################################################
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.file "crt0.asm"
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.section .text
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.p2align 1,0
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__crt0_begin:
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; -----------------------------------------------------------
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; Get required system info
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; -----------------------------------------------------------
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mov #0xC000, r8 ; = DMEM (RAM) base address
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mov &0xFFFA, r1 ; = DMEM (RAM) size in byte
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; -----------------------------------------------------------
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; Minimal required hardware setup
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; -----------------------------------------------------------
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mov #0, r2 ; clear status register & disable interrupts
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add r8, r1 ; r1 = stack pointer = end of RAM
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sub #2, r1 ; address of last entry of stack
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mov #0x4700, &0xFFB8 ; deactivate watchdog
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; -----------------------------------------------------------
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; Initialize all IO device registers (set to zero)
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; -----------------------------------------------------------
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; This loop does not trigger any operations as the CTRL registers, which are located
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; at offset 0 of the according device, are set to zero resulting in disabling the
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; specific device.
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mov #0xFF80, r9 ; beginning of IO section
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__crt0_clr_io:
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tst r9 ; until the end -> wrap-around to 0
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jeq __crt0_clr_io_end
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mov #0, 0(r9) ; clear entry
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incd r9
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jmp __crt0_clr_io
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__crt0_clr_io_end:
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; -----------------------------------------------------------
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; Clear complete DMEM (including .bss section)
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; -----------------------------------------------------------
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__crt0_clr_dmem:
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cmp r8, r1 ; base address equal to end of RAM?
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jeq __crt0_clr_dmem_end
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mov #0, 0(r8) ; clear entry
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incd r8
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jmp __crt0_clr_dmem
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__crt0_clr_dmem_end:
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; -----------------------------------------------------------
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; Copy initialized .data section from ROM to RAM
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; -----------------------------------------------------------
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mov #__data_start_rom, r5
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mov #__data_end_rom, r6
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mov #__data_start, r7
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__crt0_cpy_data:
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cmp r5, r6
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jeq __crt0_cpy_data_end
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mov @r5+, 0(r7)
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incd r7
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jmp __crt0_cpy_data
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__crt0_cpy_data_end:
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; -----------------------------------------------------------
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; Re-init SR and clear all pending IRQs from buffer
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; -----------------------------------------------------------
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mov #(1<<14), r2 ; this flag auto clears
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; -----------------------------------------------------------
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; Initialize all remaining registers
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; -----------------------------------------------------------
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mov #0, r4
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; mov #0, r5 ; -- is already initialized
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; mov #0, r6 ; -- is already initialized
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; mov #0, r7 ; -- is already initialized
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; mov #0, r8 ; -- is already initialized
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; mov #0, r9 ; -- is already initialized
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mov #0, r10
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mov #0, r11
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mov #0, r12 ; set argc = 0
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mov #0, r13
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mov #0, r14
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mov #0, r15
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; -----------------------------------------------------------
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; This is where the actual application is started
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; -----------------------------------------------------------
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__crt0_start_main:
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call #main
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; -----------------------------------------------------------
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; Go to endless sleep mode if main returns
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; -----------------------------------------------------------
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__crt0_this_is_the_end:
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mov #0, r2 ; deactivate IRQs
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mov #0x4700, &0xFFB8 ; deactivate watchdog
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mov #(1<<4), r2 ; set CPU to sleep mode
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nop
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.Lfe0:
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.size __crt0_begin, .Lfe0-__crt0_begin
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