Overview

The Momentum for Control Expert platform lets you use both IEC and LL984 programming languages when programming your control network projects. When programming your project in Control Expert, take note of the following programming rules.

Locating Double-Register Variables at an Even-Numbered Address

When declaring and locating variables that are double-word data types – for example DINT, DWORD, REAL, and UDINT – you need to locate the variable beginning at an even-numbered memory address.

Timing the Execution of XXMIT and L9_XMIT Function Blocks

Your Control Expert application program may contain a multiple of XXMIT or L9_XMIT function blocks. However, the 171 CBU 78090, 171 CBU 98090, or 171 CBU 98091 processor can execute only one of these blocks at a time per channel. If your program contains multiple blocks of this type, you may need to insert a delay into your program – or test the DONE output before activating another block. In this way, you can avoid the simultaneous execution of these blocks.

Configuring the Port Number Parameter for XXMIT and L9_XMIT

When specifying a port number for the L9_XMIT and XXMIT blocks, use the appropriate channel setting for the 171 CBU 78090, 171 CBU 98090, or 171 CBU 98091 processor. Channel setting values are:

  • 0, representing the MB1/channel 0 configurable RS232/RS485 serial port

  • 1, representing the MB2/channel 1 fixed RS485 serial port

Location of Output Data from the XXMIT Block

Control Expert writes XXMIT block output data to the memory location specified in word 5 of the MsgOut parameter. In this respect, Control Expert XXMIT block behavior mirrors that of the L9_XMIT block in Concept and Proworx.

NOTE: The behavior of the XXMIT block for other platforms, for example Quantum, is different than for Momentum In the case of Quantum, for example, XXMIT block output data is written to the location specified by the MsgIn parameter.

State RAM Objects Index Range for Modbus Server

The state RAM objects %I, %M, %IW, and %MW each has an index starting at 0. In the CPU configuration screen, when the number of objects is entered – for example 256 – the object index range is [0...(number-1)] or in this example [0...255].

Modbus server allows access of state RAM objects starting at index 1, for example [1...255]. Therefore, if you want to have 256 objects accessible with Modbus requests, you need to enter 257 in the CPU configuration screen.

Locating 32-Bit Words on Even-Numbered Word Boundary

When assigning a 32-bit variable a memory location, or otherwise locating a 32-bit double word, you need to locate the variable or word to begin on an even word boundary.