Specifications
Positioning IP 240
c) Synchronization with an external control signal
When this method is used, each positive signal edge at the IN input resets the actual value and
reactivates the position last selected. Positioning can thus be started in dependence on the IN
signal.
This method of synchronization is particularly suitable for length measurement, as the current
actual value is stored as final value on a negative signal edge at the IN input.
Note that a complete module firmware cycle may intervene between the presence of the
edges and processing of the edge change on the IP 240.
Any of these methods may be used. Each time synchronization takes place, the actual value is set
to the value of the last zero offset that was transferred, thus redefining the reference point for
the actual value.
10.2 Configuring the IP's Performance Characteristics
Sections 10.3 to 10.10 describe how to program the IP's performance characteristics, and also pro-
vide information on
• the data areas that are transferred to the IP 240 during configuring,
• how you must specify this data and
• how the data is evaluated on the IP 240.
To help you find the various configuring parameters easily and quickly, the relevant parameter is
shown in parentheses in the section headers.
Standard function block FB 167 must be used to configure the IP 240 for ”positioning” mode. As
this function block (FB) handles data interchange with the IP via a data block (DB), you must
create this data block and enter the data to be transferred before invoking the FB.
You will find
• a summary of the contents of the data block in Section 10.23.1
• a summary of the parameters for FB 167 in Section 10.23.2
10.3 Numerical Representation
When you configure the IP 240, you can decide whether you want to work with binary or BCD
numbers.
Binary representation
You can use binary numbers for all data required in positioning mode.
Signed binary numbers may assume positive or negative values. A negative value is represented as
two's complement. The signal state of the most significant bit identifies the sign of the number.
The sign bit is ”0” for a positive and ”1” for a negative number. All bit positions not needed to
represent the number assume the value of the sign bit. These bits, and the sign bit, are referred to
in the following as sign extension (SE).
Unsigned binary numbers are interpreted as absolute values, i.e. the most significant bit is also
taken as part of the value.
10-10
EWA 4NEB 811 6120-02a