84 lines
5.2 KiB
ArmAsm
84 lines
5.2 KiB
ArmAsm
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/* ################################################################################################# */
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/* # << NEORV32 - Blink LED - Assembly-Only Demo Program >> # */
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/* # ********************************************************************************************* # */
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/* # BSD 3-Clause License # */
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/* # # */
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/* # Copyright (c) 2023, 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 NEORV32 Processor - https://github.com/stnolting/neorv32 (c) Stephan Nolting # */
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/* ################################################################################################# */
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/**********************************************************************//**
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* @file demo_blink_led_asm/main.S
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* @author Stephan Nolting
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* @brief Simple assembly-only demo program. Implements a simple counter that
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* uses the lowest 8 bits of the GPIO's output port. The CPU cycle counter is
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* used as time base. Hence, this program requires the GPIO controller and the
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* CPU Zicsr and Zicnt ISA extensions.
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**************************************************************************/
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.file "main.S"
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.section .text
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.balign 4
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.global main
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// Memory map
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.set GPIO_OUTPUT_LO, 0xFFFFFC00U // address of GPIO
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.set SYSINFO_CKLK, 0xFFFFFE00U // address of SYSINFO
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/**********************************************************************//**
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* Entry point = main
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**************************************************************************/
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main:
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li a0, GPIO_OUTPUT_LO+8 // address of the GPIO.OUTPUT_LO register
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li a1, 0 // clear counter
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loop:
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andi a1, a1, 0xff // mask: just keep the lowest 8 bits
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sw a1, 0(a0) // output current counter
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call delay // call delay subroutine
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addi a1, a1, 1 // increment counter
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j loop
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/**********************************************************************//**
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* Delay subroutine using mcycle (waiting for 0.25s)
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**************************************************************************/
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delay:
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li t0, SYSINFO_CKLK+0 // address of SYSINFO.CLK
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lw t0, 0(t0) // read SYSINFO.CLK (= CPU clock speed in Hz = tick per second)
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srli t0, t0, 2 // = ticks per 0.25 seconds
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csrw mcycle, zero //clear cycle counter (low word)
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delay_loop:
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csrr t1, mcycle // get current cycle counter (low word)
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bltu t1, t0, delay_loop // restart loop if mcycle < t0
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ret // return to main
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.end
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