DF-1 Protocol
DF-1 / DF1 protocol is an asynchronous byte-oriented protocol that is used to communicate with most Allen Bradley RS232 interface modules. DF1 protocol consists of link layer and application layer formats. Link layer serial frame is a composition of conventional RS-232 serial frame with the parameters specified as 8 data bits, no parity, and a maximum baud rate of 19200. DF1 is ASCII character oriented protocol and 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.
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- 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
