Learn Multi platform Risc-V Assembly Programming... For Open Source CPUs!

Simple Samples Series

Lesson S1 - Reading and Showing a Register
Lets take a look at a Simple RISC-V program, which will read in a hex value from the keyboard, and show it back to the screen!

ShowReg.asm

Showing a register

We've built upon the code of the previous 'Hello world' example.

The start of the 'ShowRegA1' subroutine starts by showing a text label for the output.
We need to show 8 hexadecimal characters (8 four-bit nibbles) for our 32 bit register value.

We use A3 to store the remaining bits to show, and A0 to contain the nibble we're working on.

We add ASCII '0' to the value in A0, and add 7 to correct the value, if we're trying to show letters A-F.
Once we've shown the 8 characters, we finish with a space and return from our subroutine.
Printing characters is performed by another ECALL. We use ECALL 11 to output a character from A0 to the console.

Reading a register

We need to read in 8 characters. We use ECALL 12 to read in a character from the keyboard into register A0.
We need to convert this from ASCII to a hexadecimal value from 0-15 (0-F).
We shift this nibble into our final register (A1) and repeat until we've done all 8 characters. We return once we're done.
Here are the results of our tests.


This is only a simple example, but you now have the ability to read from the keyboard into a register, and write a register back to the screen.

This should allow you to 'try out' various RISC-V commands and see their results... so what are you waiting for... Get experimenting!


 

View Options
Default Dark
Simple (Hide this menu)
Print Mode (white background)

Top Menu
***Main Menu***
Youtube channel
Patreon
Email Newsletter
Merch Store
Amazon Affiliate Link
Forum
AkuSprite Editor
Dec/Bin/Hex/Oct/Ascii Table

Alt Tech
Archive.org
Bitchute
Odysee
Rumble
DailyMotion
Please note: I wlll upload more content to these alt platforms based on the views they bring in

Z80 Content
***Z80 Tutorial List***
Learn Z80 Assembly (2021)
Learn Z80 Assembly (old)
Hello World
Advanced Series
Multiplatform Series
Platform Specific Series
ChibiAkumas Series
Grime Z80
Z80 Downloads
Z80 Cheatsheet
Sources.7z
DevTools kit
Z80 Platforms
Amstrad CPC
Elan Enterprise
Gameboy & Gameboy Color
Master System & GameGear
MSX & MSX2
Sam Coupe
TI-83
ZX Spectrum
Spectrum NEXT
Camputers Lynx

6502 Content
***6502 Tutorial List***
Learn 6502 Assembly
Advanced Series
Platform Specific Series
Hello World Series
Grime 6502
6502 Downloads
6502 Cheatsheet
Sources.7z
DevTools kit
6502 Platforms
Apple IIe
Atari 800 and 5200
Atari Lynx
BBC Micro
Commodore 64
Commodore PET
Commander x16
Super Nintendo (SNES)
Nintendo NES / Famicom
PC Engine (Turbografx-16)
Vic 20

68000 Content
***68000 Tutorial List***
Learn 68000 Assembly
Hello World Series
Platform Specific Series
Grime 68000
68000 Downloads
68000 Cheatsheet
Sources.7z
DevTools kit
68000 Platforms
Amiga 500
Atari ST
Neo Geo
Sega Genesis / Mega Drive
Sinclair QL
X68000 (Sharp x68k)

8086 Content
Learn 8086 Assembly
Platform Specific Series
Hello World Series
8086 Downloads
8086 Cheatsheet
Sources.7z
DevTools kit
8086 Platforms
Wonderswan
MsDos

ARM Content
Learn ARM Assembly
Learn ARM Thumb Assembly
Platform Specific Series
ARM Downloads
ARM Cheatsheet
Sources.7z
DevTools kit
ARM Platforms
Gameboy Advance
Nintendo DS
Risc Os

Risc-V Content
Learn Risc-V Assembly
Risc-V Downloads
Risc-V Cheatsheet
Sources.7z
DevTools kit

MIPS Content
Learn Risc-V Assembly
MIPS Downloads
MIPS Cheatsheet
Sources.7z
DevTools kit

PDP-11 Content
Learn PDP-11 Assembly
PDP-11 Downloads
PDP-11 Cheatsheet
Sources.7z
DevTools kit

TMS9900 Content
Learn TMS9900 Assembly
TMS9900 Downloads
TMS9900 Cheatsheet
Sources.7z
DevTools kit
TMS9900 Platforms
Ti 99

6809 Content
Learn 6809 Assembly
Learn 6309 Assembly
6809 Downloads
6809/6309 Cheatsheet
Sources.7z
DevTools kit
6809 Platforms
Dragon 32/Tandy Coco
Fujitsu FM7
TRS-80 Coco 3
Vectrex

65816 Content
Learn 65816 Assembly
65816 Downloads
65816 Cheatsheet
Sources.7z
DevTools kit
65816 Platforms
SNES

eZ80 Content
Learn eZ80 Assembly
eZ80 Downloads
eZ80 Cheatsheet
Sources.7z
DevTools kit
eZ80 Platforms
SNES

Work in Progress
IBM370
Super-H
PowerPC
ChibiAndroids

Misc bits
Ruby programming









Buy my Assembly programming book
on Amazon in Print or Kindle!


Buy my Assembly programming book



Available worldwide!
Search 'ChibiAkumas' on
your local Amazon website!
Click here for more info!












































































































Buy my Assembly programming book
on Amazon in Print or Kindle!


Buy my Assembly programming book



Available worldwide!
Search 'ChibiAkumas' on
your local Amazon website!
Click here for more info!