#!/usr/bin/python3


# Address space is 0x00 00 - 0x07 FF or 0 - 2047
# Address bits
# 0000 0000 0000 0000
# xxxx x        - unused
# .... .n       - Mode switch 0 positive 1 = twos complement
# .... ..nn     - Digit select 00 = ones, 01 = tens, 10 = hundreds, 11 = sign
# .... .... nnnn nnnn   - Value

# Two's Complement
# 0-127 as positive
# -128  1000 0000   0x80
# -1    1111 1111   0xFF

# Data bits
# Dabc defg     - Segments on display

digits = [ 0x7E, 0x30, 0x6D, 0x79, 0x33, 0x5B, 0x5F, 0x70, 0x7F, 0x7B ]

rom = bytearray([0x00] * 2048)

# Positive values with leading zeros
# For i in range(0-255)
# Ones place 0-9 repeating over 0x00 00 - 0x00 FF   digits[ i        % 10   ]
# Tens place 0-9 repeating over 0x01 00 - 0x01 FF   digits[ int(i / 10)  % 10   ]
# Hundreds   0-9 repeating over 0x10 00 - 0x10 FF   digits[ int(i / 100) % 10   ]
# Sign 0x03 00 - 0x03 FF - everything initialized to 0x00

# Positive values without leading zeros
# Ones:     0x00 00 - 0x00 FF = digits[i % 10]

for i in range(0x00,(0xFF + 1)):
    rom[i] = digits[i % 10]

# Tens:     0x01 0A - 0x01 FF = digits[ int(i / 10) % 10]

    if(i >= 0x0A):
        rom[i + 0x100] = digits[int(i / 10) % 10]

# Hundreds: 0x02 64 - 0x02 FF = digits[int(i / 100) % 10]

    if(i >= 0x64):
        rom[i + 0x200] = digits[int(i / 100) % 10]

# Sign:  Do nothing for rom[i + 0x0300]

# ------------------

# Two's Complement
# Ones: 0x04 xx, Tens: 0x05 xx, Hundreds: 0x06 xx, Sign 0x07 xx
# 0000 01xx 0000 0000   = 0 Ones: rom[0x04 00 - 0x04 7F]
# 0000 01xx 0000 0001   = 1
# 0000 01xx 0111 1111   = 127
# 0000 01xx 1000 0000   = -128  0x80
# 0000 01xx 1111 1111   = -1

def twoComp(number):
    return 0xff & -number
    # This returns positive integers corresponding to 0x80 = 128 and 0xFF = 1
    # which can be chopped up by the usual dividing by ten and 100 to get the
    # right digits to display, and the sign digit is just always set

for i in range(0x00,(0x7F + 1)):
# Positive ones digit
    rom[i + 0x0400] = digits[i % 10]

# Positive tens digit
    if(i >= 0x0A):
        rom[i + 0x500] = digits[int(i / 10) % 10]

# Positive hundreds digit
    if(i >= 0x64):
        rom[i + 0x600] = digits[int(i / 100) % 10]

# Positive sign digit do nothing 0x0700 - 0x077F

for i in range(0x80,(0xFF + 1)):
# Negative ones digit
    rom[i + 0x400] = digits[twoComp(i) % 10]

# Negative tens digit
    if(i < 0xF7):
        rom[i + 0x500] = digits[int(twoComp(i) / 10) % 10]

# Negative hundreds digit
    if(i < 0x9D):
        rom[i + 0x600] = digits[int(twoComp(i) / 100) % 10]

# Negative sign 'digit' set pin D0 for the middle bar on the 7-segment
    rom[i + 0x700] = 0x01

# -----------------


with open('out.bin','wb') as out:
    out.write(rom)