# XMODEM

The unit at [com/xmodem.fs] implements the XMODEM/CRC protocol. It does so by
providing a [io/stream] that transparently handles the underlying handshaking.
This stream needs another stream to wrap, which is its communication line. For
example, an appropriate stream to wrap would be "com1" from [drv/pc/com].

The stream provided by this unit is called "xmodem". When you read from it for
the first time, it sends its "C" char, waiting for packets. Then, it expects a
stream of packets until EOT.

When you write to it, it waits for the other side to send its "C" char, then
sends a stream of packet until you call "close" on the stream, which flushes the
current partial packet and send EOT.

Closing the stream doesn't prevent it from being reused, it simply ends the
current XMODEM transaction.

## Example usage

  needs drv/pc/com com/xmodem
  com$
  com1 xmodem$
  console xmodem spit \ spit whatever is coming in until EOT packet
  xmodem f"init.fs" spitcloseboth \ send "init.fs" through XMODEM

## API

## Constants

xmodem  Stream exposing this unit's functionality

## Words

xmodem$ ( commstream -- )
  Initialize unit by specifying the stream it should wrap.