Introduction

Use the CPU Configuration tab to:

  • configure CPU start-up options

  • specify the size for different types of memory allocations

  • click the Viewer button to open the State RAM Viewer

Accessing the Configuration Screen

Open the CPU configuration screen as follows:

Step

Action

1

In the Project Browser , expand the Configuration and Momentum Bus nodes, and select the CPU processor (in this example, the 171 CBU 98091 processor):

2

Using the contextual menu, select Open. The CPU properties dialog opens.

3

Select the Configuration tab.

Configuring the Processor

NOTE: You can modify the parameters of this dialog box only in offline mode.

Configuration screen for CPU operation and memory management:

The CPU includes the following settings:

Setting

Description

Operating mode area

Protection of Stop command (%I)

This function is activated by an input bit. If an input bit is assigned and the function is selected, the processor cannot be stopped by using the PLC > Run/Stop command. Default = de-selected.

Memory protect

This function is activated by an input bit. If an input bit is assigned and the function is selected, it prohibits the transfer of a project into the processor and modifications in online mode. Default =de-selected.

Timer Register

The location of a %MW register to hold the value of a free running counter. The counter is incremented every 10ms while the CPU is in Run mode. The value is not incremented when the CPU is in Stop mode. Default = deselected.

Automatic start in Run

Select this to force the CPU to enter RUN mode in the event of a cold start. Default = deselected.

Initialize %MWi on cold start

On a cold start or download, if you select the check box (default):

  • The %MWi are handled like other global variables (initialized to 0 or initial value, according to the current application) in all cold start cases.

On a cold start or download, if you deselect the check box:

  • If %MW were previously saved in internal flash memory (using the %SW96 word), they are restored from internal flash memory.

  • If %MW were not saved:

    • If the cold start is linked to a power-off, the %MW are initialized.

    • If the cold start is not linked to a power-off, the current values of %MW are maintained.

NOTE: If the new (or restored) application has more %MW than the previous one, the added %MW are set to 0. (Non-zero initial values are not applied.)

Cold Start Only

Select this to force the cold start of the application, instead of the normal warm start. Default = deselected.

Memory management - State RAM area

Memory usage

The bar graph indicates the percentage of memory in use.

%M

Memory bits configurable memory size:

  • default size: 1,536

  • maximum size: 8,192

%I

Input bits configurable memory size:

  • default size: 752

  • maximum size: 8,192

%IW

Input words configurable memory size:

  • default size: 256

  • maximum size: 26,048

%MW

Memory words configurable memory size:

  • default size: 1,872

  • maximum size: 26,048

%S

System bits size (non-configurable): 128

%SW

System words size (non-configurable): 168

%KW

Constant words configurable memory size:

  • default size: 128

  • maximum size: 26,048

Setting Default and Maximum Values

You can reset the CPU configuration properties to:

  • default values

  • maximum values

The value editing window for default values and for maximum values are similar in appearance. One lists the default value for each configurable property, the other lists maximum values for each configurable property. The Default Values window:

To reset CPU configuration parameters, follow these steps:

Step

Action

1

Click one of the following command buttons on the Configuration tab:

  • Default values to reset parameters to their default values

  • Maximum values to set parameters to their maximum values

Depending on the button you push, a window opens displaying the default or maximum values for each parameter.

2

In the Default values / Maximum values window, place a check mark next to each setting you want to set to either its default of maximum value.

NOTE: You can manually place a check mark next to one parameter at a time, or click Select All to select all parameters at once.

3

Click OK to edit the selected parameter values.