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Entry type: FAQ, Entry ID: 12159065, Entry date: 11/12/2003

Specifying direct I/O access to the FM 350-2, 2 channels

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How can count and measured values be read directly by I/O access on the FM 350-2?

The FM 350-2 permits a maximum of four measured or count values to be displayed directly on the module I/O. Using the "Specify Channels" function you define which of the individual measured values is to be displayed on the I/O area.
Depending on the size of the measured or count value, you must parameterize the data format in the "User_Type " as "Word" or "Dword". If you parameterize as "Dword", only one measured or count value per "User_Type" is possible. If you parameterize "Word", you can read in two values.

In the user program, the commands L PIW for Word access and L PID for Dword access are used.
The access addresses are structured as follows:

  • For Word access: module address of the FM350-2 from HW Config. +8, +10, +12, +14
    Example: FM350-2 address is 256 à access L PIW 264, L PIW 266, L PIW 268, L PIW 270
  • For Dword access: module address of the FM350-2 from HW Config. +8, +12,
    Example: FM350-2 address is 256 à access L PID 264, L PID 268

To read out measured values in this way, the read function "FC CNT2_RD" is not necessary. The module updates its I/O input interface every 2 ms and stores the additional counted and measured values specified in the global DB of the "CNT_CTRL" function at addresses 44 to 50. To do this you need to call function FC "CNT_CTRL".
If you need more than four measured or counted values, you have to work with the read function "FC CNT2_RD" as well. Follow these steps to arrive at the parameters window "Specify channels":

  • Double-click the FM350-2 in the hardware configuration.
  • In the "Properties - FM350-2 Counter" window you press the "Parameters" button.

Fig. 1: Setting the FM350-2 properties

  • In the "FM350-2 Counter [Assigning Parameters]" window you select the menu item "Edit > Specify Channels".

Fig. 2: Specifying the channels

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