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DF1 Protocol (Full- and Half-Duplex)

DF1 Protocol (Full- and Half-Duplex)

DF1 is one of the serial RS-232 and RS-485 protocols supported by the RMC75S. This topic describes the DF1 protocol as it applies to the RMC70. For details on configuring the RMC70 for serial communications, including DF1, see the Serial RMC70S Configuration topic.


Allen-Bradley' DF1 Protocol and Command Set Reference Manual (pub. no. 1770-6.5.16) is the authority on the DF1 full- and half-duplex protocols. This manual is available on Allen-Bradleys web site (http://www.ab.com). As of this writing, the following URL contains this document: http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1770-rm516_-en-p.pdf. When this link is out-of-date, try searching for the above publication number.

Full-duplex DF1 is used for peer-to-peer communication. Therefore, only two devices can communicate with one another. The RMC70 only supports full-duplex when used with RS-232.

Half-duplex DF1 is used for master-slave communication with one or more slaves. When more than two devices communicate with one another, 2-wire RS-485 is used. Otherwise, any line driver can be used.

RMC70 Support for DF1

Both full- and half-duplex DF1 use the same application protocol, which consists of commands and functions for the slave or peer to execute.

The RMC70 supports the following DF1 functions:

  • SLC Protected Typed Write with 2 Address Fields (CMD=0x0F, FNC=0xA9)

  • SLC Protected Typed Read with 2 Address Fields (CMD=0x0F, FNC=0xA1)

  • SLC Protected Typed Write with 3 Address Fields (CMD=0x0F, FNC=0xAA)

  • SLC Protected Typed Read with 3 Address Fields (CMD=0x0F, FNC=0xA2)

  • Echo (CMD=0x06, FNC=0x00)

  • Diagnostic Status (CMD=0x06, FNC=0x03)

  • PLC-5 Word Range Read (CMD=0x0F, FNC=0x 68)

  • PLC-5 Word Range Write (CMD=0x0F, FNC=0x 67)

  • PLC-5 Typed Read (CMD=0x0F, FNC=0x 01)

  • PLC-5 Typed Write (CMD=0x0F, FNC=0x 00)

PLC Support for DF1

DF1 is a major industrial serial protocol supported by a large number of devices, both those built by Allen-Bradley and other companies. Any DF1 master implementation that uses the above blocks should also be able to read and write from the RMC70.

Using DF1 with Allen-Bradley PLCs

See the Using Allen-Bradley Controllers via Message Block for details on communicating with Allen-Bradley PLCs.


See Also

Serial Overview

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