DF1 (Allen Bradley) Addressing

This topic describes the Allen-Bradley DF1 addressing format as used by the RMC for the following communications:

• CSP or EtherNet/IP with the RMC75E, RMC150E, or RMC200

• DF1 (Full- and Half-Duplex) with the RMC75S.

Finding DF1 Addresses for RMC Registers

When configuring the host controller (such as a PLC or HMI) to communicate with an RMC, you will need to enter the DF1 addresses of the RMC's registers that you wish to read from or write to.

Ways to find RMC addresses:

1. In RMCTools editors:
   Some register addresses are displayed in RMCTools, such as in the Reg # column in Axis Tools, Indirect Data Map, and the Variable Table. To view those addresses in various formats, in the Reg# column, right-click the address and choose Address Formats.

2. Use the Address Maps in RMCTools to browse all the register addresses for any addressing method.

3. Use the Register Map help topic to browse all the register addresses for any addressing method.

RMC75 and RMC150 DF1 Addresses

The DF1 address format uses the same two-level numbering as the RMC's IEC addresses. Any RMC2 DF1 address can be accessed as an F or L register. L register addressing is useful for DINTs and DWORDS.The format for the registers in the RMC is:

Fn.x or Ln:x

where n = File number and x = the register number.

Example

For the RMC75, F8:8 is the Axis 0 Actual Position, and F8:0 (or L8:0) is the Axis 0 Status.

Supported File Types

The RMC uses F and L files for the DF1 protocol. The DF1 protocol specifies F files as 32-bit floating point registers and L files 32-bit integers.

Every register in the RMC can be addressed as either an L or F file register. Typically, it only makes sense to address REAL registers in the RMC as F file registers, and address DINT or DWORD registers as L file registers.

Since the only AB PLC at the time of this writing to support L files is the MicroLogix, you may have to set up the DF1 communications on your host system as if the RMC were a MicroLogix if you wish to use L file addressing.

Internal versus External Data Types

Notice that some RMC75 and RMC150 registers have different data types depending on whether they are accessed from user programs or externally, such as from a PLC. The RMC150 Register Map and RMC75 Register Map topics list the external and internal data types of the registers. The RMC200 does not have separate internal and external data types.

RMC200 DF1 Addresses

The RMC200 DF1 addressing includes the pre-defined addresses as listed below. The remaining DF1 addresses may be configured in the Address Maps.

Any RMC200 DF1 address can be accessed as an F or L register. L register addressing is useful for DINTs and DWORDS.

Some registers can be addressed with two different addresses, depending on whether the communication master device can address only 256 elements per file, or up to 1024 or 4096 elements per file. For example, axis 24 command area starts at F12:240 or F13:0, and variable 512 can be addressed as F20:512, or as F22:0.

Addressing Individual Bits

Some RMC registers contain individual bits that you may wish to address. The DF1 address format for a specific bit is shown below. Notice that many host controllers cannot address individual bits in an F file.

Fn.x/b or Ln:x/b, where n and x are defined above, and b = bit number.

Note:
The RMC does not support reading or writing of individual bits. You must read or write an entire 32-bit word. Some HMIs allow individual bit addressing as described above, but still read the entire word.

Example

In the RMC75, the user would like the address for the Enable Output Status Bits on axis 0. Then,

n = 8, the file number for Axis 0 Status registers,

x = 0, the number of the Status Bits register,

and

b = 7, the bit number for the Enable Output bit.

Therefore, the address is F8:0/7 or L8:0/7.

Discrete I/O

Discrete I/O are mapped to the Discrete I/O registers and can be addressed by addressing the bits in the register. See the RMC150 DI/O,  RMC75 DI/O, and RMC200 DI/O register map topics for the addresses of the I/O.

Example

For the RMC75, F23:0/5 references the state of discrete I/O point 5.

For the RMC150, F47:6/3 references the state of discrete input 3 in slot 0.

For the RMC200, add the discrete input or discrete output register to the Indirect Data Map, then address that register and bit from the Indirect Data Map.

Register Addresses in Integer Format

Occasionally, an address may need to be represented in integer format, for example when used in commands that contain a Master Register parameter. This section describes how to convert register addresses from the standard register representation to an integer.

RMC addresses are normally represented in the following Data Type:

Fn:x, where n = File number, and x = Element number.

Use the following equation to convert a register address to integer format, N:

N =  n * 4096 + x

Example

Register address F8:33 is 8*4096 + 33 = 32801.

See Also

Register Map Overview

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