setnex-sim 0.3.2

Setnex ISA balanced-ternary processor simulator

setnex-sim

Python simulator for the Setnex ISA — an open balanced ternary instruction set architecture. Implements the full fetch/decode/execute cycle for a 27-trit processor: 27 general-purpose registers, 5 configurable ternary logic modes (LMODE), and fixed-length R/I/J/U/B instructions. Built on tritlib.

Status

v0.3 — fully functional simulator with assembler and CLI toolchain. 46 opcodes implemented, 98% test coverage.

Implemented:

• Decoder (R, I, J, U, B formats)
• ALU (ADD, SUB, MUL, DIV, MOD, NEG, TAND, TOR, TNOT, TIMPL, CONS, ACONS, TSHIFT, TCMP, TGET, TSET, TSIGN, TABS, TMIN, TMAX)
• Configurable ternary logic via LMODE (Kleene, Łukasiewicz, Heyting, RM3, Bochvar)
• Registers (27 GPR + CSR: PC, LMODE, FLAGS, EPC, ECAUSE, EVEC, STATUS, ESAVE)
• Sparse word-addressed memory
• CPU fetch/decode/execute loop with ternary FLAGS (sign, carry)
• Branches and jumps (BEQ, BNE, BLT, BGT, BLE, BGE, BF, BRT3, JMP, JMPA, CALL)
• System instructions (CSRR, CSRW, CSRX, ECALL, IRET, TSEL)
• Text assembler (setnex-asm): .sasm → .tern, label resolution, pseudo-instructions
• Runner (setnex-run): execute .tern files with register initialisation and ternary exit status

Install

pip install setnex-sim

Or from source:

git clone https://codeberg.org/setnex/setnex-sim
cd setnex-sim
pip install -e ".[dev]"

CLI usage

Assembler

setnex-asm program.sasm -o program.tern

Runner

setnex-run program.tern --set a0=5 --print a0

Options:

• --set REG=VAL — initialise a register before execution (repeatable)
• --print REG — print a register after HALT (default: a0)
• --verbose — print all registers and cycle count

Exit status follows the ternary convention via a1 at HALT:

• a1 < 0 (N) → shell exit 1 (error)
• a1 = 0 (Z) → shell exit 0 (indeterminate)
• a1 > 0 (P) → shell exit 0 (success)

Example programs

Three example programs are provided in fixtures/:

sum.sasm : sum of integers 1..N (validates the full pipeline: LI, CMP, BF, ADD, ADDI, JMP):

setnex-asm fixtures/sum.sasm -o sum.tern
setnex-run sum.tern --set a0=5 --print a0
# a0 = 15

count_p.sasm : count P trits in a0 using TGET and BRT3:

setnex-asm fixtures/count_p.sasm -o count_p.tern
setnex-run count_p.tern --set a0=13 --print a0
# a0 = 3  (13 = +++ in balanced ternary — three P trits)

modsum.sasm : sum with sign driven by symmetric Euclidean i mod 3 ∈ {−1, 0, +1}, dispatched natively by BRT3 — a computation that has no natural binary equivalent:

setnex-asm fixtures/modsum.sasm -o modsum.tern
setnex-run modsum.tern --set a0=6 --print a0
# a0 = -2

check_sign.sasm : looks for a zero between a0 and a1, returns a1 = P if found, Z if absent, and a0 the results if a1 == P

setnex-asm fixtures/check_sign.sasm -o check_sign.tern
setnex-run check_sign.tern --set a0=3 a1=7 --print a0 --print a1
# a0 = 3
# a1 = 0
setnex-run check_sign.tern --set a0=-3 a1=7 --print a0 --print a1
# a0 = 0
# a1 = 1

Python API

from setnex_sim.cpu import CPU
from setnex_sim.assembler import encode_R, encode_I

cpu = CPU()
program = [
    encode_I(-24, rd=1, rs1=0, imm=5),   # LI r1, 5
    encode_I(-24, rd=2, rs1=0, imm=3),   # LI r2, 3
    encode_R(-40, rd=3, rs1=1, rs2=2),   # ADD r3, r1, r2
    encode_R(0,   rd=0, rs1=0, rs2=0),   # HALT
]
cpu.load(program)
cpu.run()
print(int(cpu.regs[3]))  # 8

Setnex ISA

The full ISA specification is available at setnex.org and on Codeberg — Apache 2.0, patent-free.

Licence

MIT — Copyright 2026 Eric Tellier