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✨ [sw] add assembly-only demo program #436

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Oct 27, 2022
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✨ [sw] add assembly-only demo program #436

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85 changes: 85 additions & 0 deletions sw/example/demo_blink_led_asm/main.S
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/* ################################################################################################# */
/* # << NEORV32 - Blink LED - Assembly-Only Demo Program >> # */
/* # ********************************************************************************************* # */
/* # BSD 3-Clause License # */
/* # # */
/* # Copyright (c) 2022, Stephan Nolting. All rights reserved. # */
/* # # */
/* # Redistribution and use in source and binary forms, with or without modification, are # */
/* # permitted provided that the following conditions are met: # */
/* # # */
/* # 1. Redistributions of source code must retain the above copyright notice, this list of # */
/* # conditions and the following disclaimer. # */
/* # # */
/* # 2. Redistributions in binary form must reproduce the above copyright notice, this list of # */
/* # conditions and the following disclaimer in the documentation and/or other materials # */
/* # provided with the distribution. # */
/* # # */
/* # 3. Neither the name of the copyright holder nor the names of its contributors may be used to # */
/* # endorse or promote products derived from this software without specific prior written # */
/* # permission. # */
/* # # */
/* # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS # */
/* # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF # */
/* # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE # */
/* # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, # */
/* # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE # */
/* # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED # */
/* # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING # */
/* # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED # */
/* # OF THE POSSIBILITY OF SUCH DAMAGE. # */
/* # ********************************************************************************************* # */
/* # The NEORV32 Processor - https://github.com/stnolting/neorv32 (c) Stephan Nolting # */
/* ################################################################################################# */


/**********************************************************************//**
* @file demo_blink_led_asm/main.S
* @author Stephan Nolting
* @brief Simple assembly-only demo program. Implements a simple counter that
* uses the lowest 8 bits of the GPIO's output port. The CPU cycle counter is
* used as time base. Hence, this program requires the GPIO controller and the
* CPU Zicsr and Zicnt ISA extensions.
**************************************************************************/
.file "main.S"
.section .text
.balign 4
.global main

// Memory map
.set GPIO_OUTPUT_LO, 0xFFFFFFC8U // address of the GPIO.OUTPUT_LO register
.set SYSINFO_CKLK, 0xFFFFFFE0U // address of SYSINFO.CLK


/**********************************************************************//**
* Entry point = main
**************************************************************************/
main:
li a0, GPIO_OUTPUT_LO // address of the GPIO.OUTPUT_LO register
li a1, 0 // clear counter

loop:
andi a1, a1, 0xff // mask: just keep the lowest 8 bits
sw a1, 0(a0) // output current counter
call delay // call delay subroutine
addi a1, a1, 1 // increment counter
j loop


/**********************************************************************//**
* Delay subroutine using mcycle (waiting for 0.25s)
**************************************************************************/
delay:
li t0, SYSINFO_CKLK // address of SYSINFO.CLK
lw t0, 0(t0) // read SYSINFO.CLK (= CPU clock speed in Hz = tick per second)
srli t0, t0, 2 // = ticks per 0.25 seconds
csrr t1, mcycle // get current cycle counter (low word)
add t1, t1, t0

delay_loop:
csrr t0, mcycle // get current cycle counter (low word)
bltu t0, t1, delay_loop // restart loop if mcycle < t1

ret // return to main

.end
4 changes: 4 additions & 0 deletions sw/example/demo_blink_led_asm/makefile
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# Modify this variable to fit your NEORV32 setup (neorv32 home folder)
NEORV32_HOME ?= ../../..

include $(NEORV32_HOME)/sw/common/common.mk