DF-1 Protocol
# 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
