Basic/Enhanced PROFIBUS Modes (RMC75P Only)

The RMC75P supports four additional modes that are not supported by the RMC150E: Basic, Basic+, Enhanced, and Enhanced+.

These Basic/Enhanced modes require more programming in the PLC and are typically more difficult to use than the I/O modes. Therefore, most users will prefer the I/O modes. However, the I/O modes typically require more programming in the RMC. The following table lists pros and cons of the Basic/Enhanced modes to help you choose which mode is appropriate for your application:

I/O Modes

Basic/Enhanced Modes

Advantages

Easy to understand
Requires little programming in the PLC.
Can start user programs to issue commands or read and write any registers.
Supported by both the RMC75P and RMC150E. Therefore, programs made for either RMC easily transfer to other RMC.

Advantages

Directly issue commands

Directly write to any register(s)
Directly read from any registers(s)
Does not require using the Program Triggers and User Programs

Disadvantages

Requires using the Program Triggers and/or user programs in the RMC.

Disadvantages

Can be difficult to understand
Requires a lot of programming in the PLC.
Not supported in the RMC150E. Therefore, programs made for these modes for the RMC75P do not directly transfer to the RMC150E.

Basic/Enhanced Mode Details

If you decide to use a Basic/Enhanced mode, choose from one of the following. For more details, see the topic for each respective mode.

Mode:	Basic	Basic+	Enhanced	Enhanced+
Commands* per Cycle	1	1	1	1
Simultaneous Commands
Cyclic Read Registers	8	16	8	16
Explicit Read Registers	1	1	1+7	1+7
Explicit Write Registers	1	1	1+7	1+7
Bandwidth Required (16-bit words)	16 consistent** I/O words	16 consistent I/O words + 16 consistent Input words	2 blocks of 16 consistent** I/O words	2 blocks of 16 consistent I/O words + 16 consistent Input words

*For commands with more than 5 command parameters, only the first 5 parameters will be issued. The remaining parameters will be 0. To issue such commands completely, include them in a user program and issue a command via PROFIBUS to start the user program.

**A block of PROFIBUS data is called 'consistent' if it is consistent over the length of the block, rather than just over a single 8- or 16-bit data item. Consistent blocks of data will stay together through the communication, from the time it was captured in the slave device until it is delivered to the master application, whereas data from different consistent blocks could have been sampled at different times.

For details on reading, writing and issuing commands, see the mode type you are using. For instructions on how to select a mode, see the PROFIBUS Configuration topic.

RMC Register Addresses for Basic/Enhanced Modes

When using the Basic/Enhanced modes, the RMC register addresses use the same file:element addresses as the RMC's Allen-Bradley IEC-61131 addresses.

For example, to read the Axis 0 Actual Position via PROFIBUS, its address is %MD8.8. Therefore, the address via PROFIBUS is file 8, element 8.