#!/usr/bin/env python3
# Generate .bin file with ATK16 CPU microcode

# Addressed by OOOO BUUU
# where O = opcode, B = branch flag, U = microsequencer value

import sys

if len(sys.argv) != 2:
  print("usage: ucode.py <outfile.bin>")
  sys.exit(1)

outfile_path = sys.argv[1]

PC_CO   = 0b0000_0000_0000_0001
PC_IE   = 0b0000_0000_0000_0010
PC_OE   = 0b0000_0000_0000_0100
MAR_IE  = 0b0000_0000_0000_1000
RAM_IE  = 0b0000_0000_0001_0000
RAM_OE  = 0b0000_0000_0010_0000
R1_IE   = 0b0000_0000_0100_0000
R1_OE   = 0b0000_0000_1000_0000
R2_IE   = 0b0000_0001_0000_0000
R2_OE   = 0b0000_0010_0000_0000
IR_IE   = 0b0000_0100_0000_0000
L9_OE   = 0b0000_1000_0000_0000
L12_OE  = 0b0001_0000_0000_0000
ALU_OE  = 0b0010_0000_0000_0000
HALT    = 0b0100_0000_0000_0000
US_RS   = 0b1000_0000_0000_0000

BRANCH_FLAG_STATES_N = 2
UCODE_N = 2**3
CONTROL_WORD_SIZE = 2

def not_branch(bs):
  return BRANCH_FLAG_STATES_N * [bs]

def branch(false_branch, true_branch):
  return [false_branch, true_branch]

fetch = [PC_OE|MAR_IE, RAM_OE|IR_IE|PC_CO]

def nop():
  return not_branch([*fetch, US_RS, 0, 0, 0, 0, 0])

ucode = [
  # ALU 0000 LLLR RRTT TSSS
  not_branch([*fetch, ALU_OE, US_RS, 0, 0, 0, 0]),
  # ALS 0001 LLLR RRTT TSSS
  not_branch([*fetch, ALU_OE, US_RS, 0, 0, 0, 0]),
  # LDR 0010 RRRT TTXX XXXX
  not_branch([*fetch, R1_OE|MAR_IE, RAM_OE|R2_IE, US_RS, 0, 0, 0]),
  # STR 0011 RRRT TTXX XXXX
  not_branch([*fetch, R1_OE|MAR_IE, R2_OE|RAM_IE, US_RS, 0, 0, 0]),
  # LDI 0100 RRRI IIII IIII
  not_branch([*fetch, L9_OE|R1_IE, US_RS, 0, 0, 0, 0]),
  # JMP 0101 RRRX XXXX XXXX
  not_branch([*fetch, R1_OE|PC_IE, US_RS, 0, 0, 0, 0]),
  # BR  0110 XFFR RRXX XXXX
  branch([*fetch, US_RS, 0, 0, 0, 0, 0],
         [*fetch, R2_OE|PC_IE, US_RS, 0, 0, 0, 0]),
  # NOP 0111 XXXX XXXX XXXX
  nop(),
  # NOP 1000 XXXX XXXX XXXX
  nop(),
  # NOP 1001 XXXX XXXX XXXX
  nop(),
  # NOP 1010 XXXX XXXX XXXX
  nop(),
  # NOP 1011 XXXX XXXX XXXX
  nop(),
  # NOP 1100 XXXX XXXX XXXX
  nop(),
  # NOP 1101 XXXX XXXX XXXX
  nop(),
  # NOP 1110 XXXX XXXX XXXX
  nop(),
  # HLT 1111 XXXX XXXX XXXX
  not_branch([*fetch, HALT, 0, 0, 0, 0, 0]),
]

INST_N = len(ucode)
TOTAL_BYTEARRAY_SIZE = INST_N * BRANCH_FLAG_STATES_N * UCODE_N * CONTROL_WORD_SIZE

res_b = bytearray(TOTAL_BYTEARRAY_SIZE)

for i in range(INST_N):
  for j in range(BRANCH_FLAG_STATES_N):
    for k in range(UCODE_N):
      for l in range(CONTROL_WORD_SIZE):
        idx = l + \
            k * CONTROL_WORD_SIZE + \
            j * CONTROL_WORD_SIZE * UCODE_N + \
            i * CONTROL_WORD_SIZE * UCODE_N * BRANCH_FLAG_STATES_N
        cword = ucode[i][j][k]
        assert len(ucode[i][j]) == 8
        cbyte = (cword >> (8 * (CONTROL_WORD_SIZE - l - 1))) & 0xff
        print(f"inst: {i:>04b}, idx: {idx:>04x}, cbyte: {cbyte:>08b}")
        res_b[idx] = cbyte

with open(outfile_path, "wb") as f:
  f.write(res_b)