title: DF-1 Protocol
text: # DF-1 Protocol
  
  DF-1 / DF1 protocol is an asynchronous byte-oriented protocol that is used to communicate with most Allen Bradley RS-232 interface modules. DF1 protocol consists of link layer and application layer formats. DF1 works over half duplex and full duplex modes of communication.
  
  ## Application layer messages
  
  Application layer message format consists of Command Initiator messages (request messages) and Command Executor (reply messages). Important command initiator messages are as follows.
  
  * apply port configuration
  * bit write
  * change mode
  * close file
  * diagnostic status
  * disable forces
  * disable outputs
  * download request
  * echo
  * enable outputs
  * enable PLC scanning
  * enter download mode
  * enter upload mode
  * exit download/upload mode
  * file read
  * file write
  * get edit resource
  * initialize memory
  * modify PLC-2 compatibility file
  * open file
  * physical read
  * physical write
  * read bytes physical
  * read diagnostic counters
  * reset diagnostic counters
  * read link parameters
  * read-modify-write
  * read section size
  * restart request
  * set CPU mode
  * set data table size
  * set ENQs
  * set link parameters
  * set NAKs
  * set timeout
  * set variables
  * shutdown
  