Материал: m012900e

232 • I/O modules

SSI transmitter interface 750-630

The resolution of the sensor depends upon the configuration of the sensor and the physical number of revolutions in the motion profile. Since the basis of the encoder is to provide absolute positional information, which is based upon a mechanical configuration limited to one revolution or less, the maximum resolution of this module is 24 bit.

The frequency of the data signal input to the SSI module is maintained at 125 kHz.

Listed below are the recommended cable lengths for the various clock signal Baud rates

Attention

For the process data configuration of these bus modules please refer to chapter "Process data architecture for MODBUS/TCP" in the process image description of the corresponding coupler/controller.

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I/O modules • 233

Incremental-encoder-interface 750-631

4.7.1.1.2 Incremental encoder interface 750-631

Technical description

Attention

The description that is in the I/O ring binder data pages (888-543/020-101 dated 4/96) is not correct.

This technical description is only valid for hardware and software versions X X X X 2 B

0 1----. The product series number is printed on the right side of the module.

The described operational mode is 4 times or quadrature sampling.

The following description is preliminary and is applicable to the factory configuration.

The Quadrature Encoder Interface can operate with all WAGO-I/O-SYSTEM buscouplers (except for the economy type).

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234 • I/O modules Incremental-encoder interface 750-631

Operational Characteristics:

The quadrature encoder interface accepts up to two input signals for the counting increment. The index pulse may also be considered should the control configuration require it. There is also a Latch and Gate input available on the module for added functionality.

The quadrature encoder provides two signals that are shifted 90 degrees from each other, signals A and B. In order to achieve a better common mode noise rejection ratio, the output signals from the encoder are transmitted via a differential signal. Their complement signals, A(inv.) and B(inv.) are also transmitted. A directional determination may be made by which signal leads. If the A signal leads, the direction is considered to be forward. If the B signal leads, the direction is considered to be reverse.

By exchanging the A and A(inv.) the phase relationship will be changed by 180 degrees, thus allowing the direction to be preset via the wiring configuration.

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I/O modules • 235

Incremental-encoder-interface 750-631

Most quadrature encoders have an Index signal, or Z rev, as well as the incremental signal. This signal provides one pulse per revolution with a duration equal to an incremental pulse.

The inputs to the quadrature encoder module must be supplied from an encoder with Line Driver Outputs for proper operation. The 5 Volt DC output may be used to power the encoder. The 24 Volt DC input supply must be provided from an external power supply.

The Gate and Latch inputs are 24 Volt DC.

Module Inputs and Outputs:

The Input Gate stops the counter. Only 0 V or an open connection will initialize the counter.

24 V stops the counting process.

The input Latch controls the writing of the actual counter value into the Latch register. This input is activated by the control bit EN_LATEXT ("1"). EN_LACT has to be deactivated ("0"). The first change from 0 V to 24 V at the Latch input writes the actual counter value into the Latch register.

The control byte has the following bits:

Please note Bit 7 is a reserved bit and must always be set to 0. It is responsible for register communication which is not described in this chapter.

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236 • I/O modules Incremental-encoder interface 750-631

The status byte contains the information as listed below.

It is possible to process and/or check the actions listed below via the control and status bits

Extending the 16 bit counting range:

The internal counting range is 16 bits or a maximum value of 65535. Should the application require an extended count range the location-difference- integration method may be employed. This method uses the control system to store the encoder module value. Any new encoder value will have the previously stored encoder value subtracted from it. This value will then be added to an accumulated register value. It is assumed that the encoder value difference of the two encoder values is smaller than 16 bits therefore overflows need not be considered.

Another method calculates the extended encoder range via the underflow and overflow status bits. The encoder value is either added or subtracted to the ac-

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