DF1 Addressing

This topic describes the Allen-Bradley DF1 addressing format as used by the RMC. For other addressing formats, see the Register Map Overview topic.

The DF1 address format must be used when communicating with the RMC75S via DF1 (Full- and Half-Duplex) and when communicating with the RMC75E or RMC150E via CSP or EtherNet/IP.

Address Format

The DF1 address 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 RMC70, 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 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 RMC70 Register Map topics list the external and internal data types of the registers.

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

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 and RMC70 DI/O register map topics for the addresses of the I/O.

Example

For the RMC70, 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.

Occasionally, an addresses may need to be represented in integer format. 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