Communicating with HMIs

The RMCs can communicate with many types of HMIs (Human-Machine Interfaces). This topic describes the protocols the HMI must support in order to communicate with each of the RMC series motion controllers. It also describes how to configure the communications and the basics of actually communicating, such as issuing commands, writing and reading, etc.

Example programs for certain HMIs are available on the downloads page of Delta's website. These can help you get up and running quickly.

Requirements of the HMI

Requirement 1: Must Support a Compatible Protocol

The HMI must support a protocol that is compatible with the specific RMC. Notice that certain protocols have specific requirements that the HMI must also fulfill.

Requirement 2: 32-bit Floating Point Support

The HMI must support 32-floating point numbers. The HMI must be able to write individual floating-point numbers and read individual floating-point numbers. In order to issue commands to the RMC, the HMI must also be able to write to multiple floating-point numbers at once.

Optional Requirement 3: Read Bits in a Register

Since the RMC does not support reading boolean data types directly, the HMI should be able to view individual bits in a register read via Modbus/TCP or Modbus/RTU, or view individual bits in an F or L register read via CSP or DF1. This allows the HMI to display status items such as Axis Enabled, Halted, etc.

Configuring the HMI Communications

Using Ethernet:

For most devices, use Modbus/TCP. If that option is not available, set up the HMI communications as if it were talking to a SLC 500 PLC using CSP or EtherNet/IP.

For more details on setting up ethernet, see the Ethernet Overview topic.

Using Serial RS-232 or RS-485:

For most devices, use Modbus/TCP. If that option is not available, set up the HMI communications as if it were talking to a PLC. When selecting the protocol, choose an Allen-Bradley SLC 500 PLC with DF1. If the SLC500 is not available, choose a PLC-5 or a MicroLogix.

If you are connecting the HMI to the RS-232 Monitor port on the RMC75S or RMC75P, make sure the PLC communication settings are identical to the RS-232 Monitor Port settings: DF1 Full-Duplex, 38400 Baud, 8 Data Bits, No Parity, 1 Stop Bit, CRC.

If you are connecting the HMI to the communications serial port on the RMC75S, make sure you configure the RMC75S serial settings identically to the PLC communication settings.

Using the Communications

Finding and Using Register Addresses

Read and write to registers in the RMC just as you would with a PLC.

Some RMC register addresses are displayed in RMCTools, such as in the Axis Tools, Indirect Data Map, and the Variable Table. To view those addresses in various formats, right-click the address and choose Address Formats. To find other RMC addresses, use the Address Maps in RMCTools, or the Register Map help topic.

The RMCs contain only 32-bit registers. Most are floating-point registers, but some are double integers (DINT) or double words (DWORD).

Issuing Commands

Issuing commands consists of writing to the command registers. The HMI must be able to write to several registers at once. See the Issuing Commands topic for more details.

Viewing Individual Bits

The RMC supports reading entire registers, not reading individual boolean data. Therefore, to get bit data from the RMC, the HMI must be able to read an entire word and look at just one bit in the word.

Most HMIs can read individual bits from the RMC if they use Modbus/TCP or Modbus/RTU.  With the Allen-Bradley CSP or DF1 protocols, viewing individual bits may be difficult for some HMIs because the RMC registers can only be accessed as F or L register types.

Writing Individual Bits

The RMC supports writing entire registers, not reading individual boolean data. Therefore, to write individual bits, the HMI must be able to read an entire word and look at just one bit in the word. This usually involves reading the register from the RMC, modifying the bit, then writing the register back to the RMC. Many HMIs cannot do this. Therefore, in order to write a bit, you may need to create a user program in the RMC to write the bit, then have the HMI trigger the user program.

Tips on Using the RMC with an HMI as a Stand-alone System

For small machine applications, the RMC is fully capable of acting as a stand-alone system together with an HMI. Several features in the RMC make this possible for many types of systems:

• Start in RUN Mode
  The RMC can be set to start in RUN mode. It is immediately ready for motion without requiring the user to enable it from the HMI. See the Run/Program Mode topic for details.

• Start a User Program on Startup
  If the RMC is set to start up in RUN mode, it is possible to start a User Program immediately. This is accomplished by using the _FirstScan bit in the Program Triggers. See the Program Triggers topic for details.

• User Programs
  User Programs can perform complex motion sequences and mathematical operations. See the User Programs topic for details.

• Program Triggers
  The Program Triggers allow the RMC to respond to discrete inputs to any other condition, without requiring that the user explicitly command it to do something. See the Program Triggers topic for details.

Sample Programs

Delta's website provides sample HMI programs for communicating with the RMC. These programs demonstrate reading and writing registers and issuing commands. Using the demo programs can drastically reduce your development time.

The sample programs are available from the downloads page.

See Also

Communications Overview | Using Serial Communications

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