User Manual

9.57 Arithmetic

The Arithmetic logical device combines two numeric values by adding, subtracting, multiplying or dividing them. Both input terms may either be constant values or the actual value of any numeric parameter of another device.

Device window pages

The following table shows which device window pages are available with this individual device type. Tool-bar functions not mentioned here are described at the general description of device windows .

--- Shows the actual input output values of the device.
--- The device info page.
--- The maintenance page. The configuration parameters from this page are described below.

Configuration parameters

At the maintenance page of the device window there are a couple of configuration parameters which must be set to interconnect the Arithmetic device with the devices that deliver the input signals and to configure the device's performance.

parameter	description
arithmeticType	With this parameter you define the arithmetic operation the device shall perform.
comment	The comment is displayed with the device's output value at the device window. You may set it to describe the purpose of the computation.
input-A.Id	Enter the ID of the parameter the device shall use as input A here. Leave the field empty if input A shall be set to a constant value
input-A.constant	Enter the constant value for input A here. Leave the field empty if input A shall follow another parameter.
input-A.comment	The input A comment is displayed above value at the device window.
input-B.Id	Enter the ID of the parameter the device shall use as input B here. Leave the field empty if input B shall be set to a constant value
input-B.constant	Enter the constant value for input B here. Leave the field empty if input B shall follow another parameter.
input-B.comment	The input B comment is displayed above value at the device window.

Remarks

The device uses A as the first, B as the second operand. Thus SUB calculates a-b , DIV calculates a/b .
If a division by zero error occurs, the device does not claim this and leaves the output value unchanged.
Never use the device's output parameter as one of the inputs. This feed-back will cause an endless recursion which in fact will eat up all available CPU power and memory.
The device 'learns' the number of fraction digits to display at the main page from the connected parameter's definition. The number format of input A also is used to display the output value. If you re-configure an input from constant to parameter-ID and vice versa you may need to restart the software in order to get the number format displayed correctly.
Connecting the device to non-numeric parameters (textual parameters, multiple choice parameters) will lead to unpredictable results.

Variables defined by this device driver

name	type	flags	range
info.driver	TEXT	R/O	StringRange R/O
info.type	TEXT	R/O	StringRange R/O
info.frame	TEXT	R/O	StringRange R/O
config.arithmeticType	CHOICE	SAVE SETUP	EnumRange (ADD SUB MUL DIV)
config.comment	TEXT	SAVE SETUP	StringRange
config.input-A.Id	TEXT	SAVE SETUP	StringRange
config.input-A.constant	TEXT	SAVE SETUP	StringRange
config.input-A.comment	TEXT	SAVE SETUP	StringRange
config.input-B.Id	TEXT	SAVE SETUP	StringRange
config.input-B.constant	TEXT	SAVE SETUP	StringRange
config.input-B.comment	TEXT	SAVE SETUP	StringRange
output	FLOAT	R/O	DoubleRange R/O (0.000 .. 0.000)
a	FLOAT	R/O	DoubleRange R/O (0.000 .. 0.000)
b	FLOAT	R/O	DoubleRange R/O (0.000 .. 0.000)