Open Source Instruction Set Architecture
Learn about the revolutionary open-source RISC-V instruction set architecture. Explore processor design, assembly programming, system-on-chip development, and hands-on experience with RISC-V development tools and FPGA implementation.
No licensing fees, vendor lock-in, or restrictive patents
RISC-V follows classic RISC design principles with modern improvements, focusing on simplicity, modularity, and extensibility.
RISC-V supports multiple base integer ISAs optimized for different applications and performance requirements.
RISC-V's modular design allows adding standardized extensions for specific functionality without breaking compatibility.
As an open standard, RISC-V eliminates licensing fees and vendor lock-in, fostering innovation and customization.
Register-register operations (add, sub, xor, etc.)
Example: add x1, x2, x3 → x1 = x2 + x3
Immediate operations and loads (addi, lw, etc.)
Example: addi x1, x2, 100 → x1 = x2 + 100
Store operations (sw, sh, sb)
Example: sw x2, 8(x1) → Memory[x1 + 8] = x2
# Basic arithmetic operations
addi x1, x0, 10 # x1 = 10
addi x2, x0, 20 # x2 = 20
add x3, x1, x2 # x3 = x1 + x2 = 30
sub x4, x2, x1 # x4 = x2 - x1 = 10
mul x5, x1, x2 # x5 = x1 * x2 = 200
div x6, x2, x1 # x6 = x2 / x1 = 2# Memory load and store operations
lui x1, 0x10000 # Load upper immediate
addi x2, x0, 42 # x2 = 42
# Store word to memory
sw x2, 0(x1) # Memory[x1] = x2
sw x2, 4(x1) # Memory[x1+4] = x2
# Load word from memory
lw x3, 0(x1) # x3 = Memory[x1]
lw x4, 4(x1) # x4 = Memory[x1+4]# Simple loop to sum numbers 1 to 10
addi x1, x0, 1 # counter = 1
addi x2, x0, 10 # limit = 10
addi x3, x0, 0 # sum = 0
loop:
add x3, x3, x1 # sum += counter
addi x1, x1, 1 # counter++
ble x1, x2, loop # if counter <= limit, loop
# Result: x3 contains sum (55)
# Function call example
jal x1, function # call function, save return address
function:
# Function body
addi x10, x10, 1 # increment argument
jalr x0, x1, 0 # returnThe simplest RISC-V processor executes one instruction per clock cycle, with direct connections between functional units.
Pipelined processors overlap instruction execution stages to improve throughput while handling data and control hazards.
Complete SoC designs integrate RISC-V cores with peripherals, memory controllers, and I/O interfaces.
RISC-V designs can be rapidly prototyped and tested on FPGA platforms before ASIC implementation.