def boot_hp(p, /, *, addr=0o10000):
    """Read the first 1KB of drive 0 into location 'addr'."""

    # this is the sort of thing that would be keyed in from
    # the console switches (if the machine was not equipped
    # with a boot rom option to hold it instead)
    #
    # It is a minimalist  program, with lots of assumptions, to  read 1K
    # from block zero of drive 0 into location 0. The execution start
    # at zero is done elsewhere.
    #
    # NOTE WELL: THIS ASSUMES THE MACHINE IS IN RESET CONDITION WHICH
    #            MEANS MANY OF THE DEVICE REGISTERS ARE ASSUMED TO BE ZERO
    #
    #      MOV #176704,R0       -- note how used
    #      MOV #177000,-(R0)    -- word count - read 1K though boot really 512
    #      MOV #071,-(R0)       -- go!
    program_insts = (
        0o012700,          # MOV #0176704,R0
        0o176704,
        0o012740,          # MOV #177000,-(R0)
        0o177000,
        0o012740,          # MOV #071, -(R0)
        0o000071,
        0o0,               # HALT
    )

    for o, w in enumerate(program_insts):
        p.physRW(addr + o + o, w)

    return addr


def boot_file(p, fname, /, *, addr=0, little_endian=True, skipwords=8):
    """Read a raw binary image of pdp11 data into location 'addr'."""

    with open(fname, 'rb') as f:
        bb = f.read()

        # Two data format cases:
        #   1) little_endian (the default)
        #
        #      The file is truly a binary image of pdp11 format data
        #      and the words (pairs of bytes) in bb are in little endian
        #      order. They will be assembled accordingly and the names
        #      "low" and "hi" make sense.
        #
        #   2) not little_endian
        #
        #      Presumably the file has been byte-swapped already and
        #      the words (pairs of bytes) in it are in big endian order.
        #      They will be assembled accordingly, but the names "low"
        #      and "hi" are backwards.
        #

        xi = iter(bb)
        words = []
        for low in xi:
            hi = next(xi)
            if little_endian:
                words.append((hi << 8) | low)
            else:
                words.append((low << 8) | hi)    # see case 2) above

        for a, w in enumerate(words[skipwords:]):
            p.physmem[a] = w
    return p


if __name__ == "__main__":
    import time
    from machine import PDP1170
    p = PDP1170(loglevel='INFO')
    pc = boot_hp(p)
    print("starting PDP11; telnet/nc to localhost:1170 to connect to console")
    print("There will be no prompt; type 'boot' to start boot program")
    p.run(pc=pc)
    # technically need to confirm the drive is RDY, i.e., the read
    # completed, but using a delay is a lot simpler and works fine.
    # In real life, humans would have manipulated console switches to
    # start execution at location 0, which is also a source of delay. :)
    time.sleep(0.05)
    p.run(pc=0)