# Tips on XMODEM

## 8bit clean

The XMODEM file transfer protocol requires the communication lines to be transparent to all 8 bit characters, from $00 to $FF.

### For serial port:

Set the appropriate parameters in the [Setup] Serial port dialog box. Data must be 8 bit, and Flow control must be hard (CTS/RTS) or none.

### For telnet:

If file transfers fail, try connecting to the host with the binary option. To connect with the binary option:

- Specify the /B option on the command line, or
- Edit the setup file.
  Telnet binary option

## padding at end of file

The XMODEM file transfer protocol handles files in blocks of 128 or 1024 bytes, and file lengths cannot be exchanged. The received data length is always a multiple of 128 or 1024 bytes.

Sender puts padding in the last block that is longer than the length of the transmitted file. The padding is $1A according to the XMODEM specification. But it may be some other value depending on the XMODEM sending program.