Specifications

IP 240 Functional Description
6 Functional Description
6.1 Module Functions
The IP 240 is an intelligent I/O module for acquiring and preprocessing encoder and counting
pulses. The module has two channels and can be initialized for the relevant application via the
user program.
6.1.1 Modes
The IP 240 can be operated in the positon decoding, counting, positioning and IP 252 expansion
modes.
The two channels of the IP 240 module can be initialized separately in the position decoding,
positioning and counting modes. In IP 252 expansion mode, both channels are assigned to this
mode.
Position decoding
In the position decoding mode, incremental encoder signals are summated to an actual value with
the correct sign, and compared cyclically to preset start-of-track and end-of-track values. The sign
of the pulses is derived from the phase displacement between encoder signals A and B. A zero
offset can be specified for the actual value.
A measuring system can be calibrated to a reference point by means of a reference point
approach.
Counting
In counting mode, positve-going signal edges at the counting input are counted in a down
counter, under gate control, starting with an initial value. Counting can be enabled by an external
gate signal or by a control bit.
Various output reactions can be logically combined when the count reaches zero. After zero, the
pulses are acquired with a negative sign when a gate signal is active.
IP 252 expansion (only S5-115U)
In the IP 252 expansion mode, the IP 240 makes both channels available to the IP 252 digital
closed-loop control module for the connection of other incremental encoders.
In this mode, the input signals are processed as for positon decoding. Data interchange between
the two I/O modules is direct.
Positioning
When the IP 240 is initialized for positioning mode, it can be used for controlled positioning with
cutoff points. Up to 254 positions per channel can be stored on the IP for this purpose. Once a
position has been selected, the IP itself can control the traversing speed or the direction of travel
over the IP outputs. Incremental decoders are used for position sensing.
Three methods of synchronization are possible in this mode. In addition, the actual value can be
matched via a zero offset.
EWA 4NEB 811 6120-02a 6-1