Siemens SIMATIC User Manual

Other signal modules
7.4 Position decoder module SM 338; POS-INPUT; (6ES7338-4BC01-0AB0)
S7-300 Module data
504 Manual, 06/2017, A5E00105505-AJ
7.4.3.4 Freeze function
The freeze function "freezes" the actual encoder values of SM 338. The freeze function is
coupled to the digital inputs DI 0 and DI 1 of SM 338.
The freeze function is triggered by a signal transition (positive edge) a DI 0 or DI 1. Bit 31 = 1
(output address) identifies a frozen encoder value. You can freeze one, two or three encoder
values using one digital input.
Enable the freeze function by setting the corresponding parameters in
STEP 7 .
To allows their event-triggered evaluation, the encoder values are retained until the freeze
function is terminated.
Terminating the freeze function
The freeze function must be terminated separately at each encoder input. You acknowledge
the function in the user program by using STEP 7 operation T PAB to set bit 0, 1 or 2 to "xyz"
according to the channel (Program example: refer to chapter "AUTOHOTSPOT").
The acknowledgement resets bit 31 of the corresponding encoder value, and initiates a
refresh of the encoder values. You can freeze the encoder values again after you cleared the
ACK bit at the output address of the module.
In isochronous mode, the acknowledgement is processed at the time T
o
. From this point on,
you can freeze the encoder values again by setting the digital inputs.
Note
The Freeze function is acknowledged automatically when you assign new parameters with
different arguments to the relevant
channel (refer to chapter "AUTOHOTSPOT").
If the parameter are identical the Freeze function remains unaffected.

Siemens SIMATIC Specifications

General

Product type designation	SIMATIC
CPU	Varies by model
Memory	Varies by model
Input/Output	Varies by model
Communication	Varies by model
Programming Language	STEP 7
Operating Temperature	0°C to 60°C (varies by model)
Protection Class	IP20
Category	Programmable Logic Controller (PLC)

Summary

Preface

General technical data

Provides an overview of general technical data for the S7-300 automation system, including standards, EMC, shipping and storage, mechanical and climatic conditions, and specifications.

Power supply modules

Details on power supply modules for the S7-300 PLC, covering characteristics, wiring diagrams, block diagrams, line protection, and reaction to atypical operating conditions.

Digital modules

Describes digital modules, including module overview, digital input modules, digital output modules, relay output modules, digital IO modules, selection and commissioning steps, programming, and diagnostics.

Principles of analog value processing

Explains the basic procedure for wiring and connecting signal sensors to analog inputs and outputs, including observations and general information on sensor wiring.

Principles of analog modules

Covers analog values for measuring or output ranges, analog value conversion, representation of values for analog input/output channels, and operational limits.

Dimensional drawings

Provides dimensional drawings of S7-300 components including mounting rails, power supply modules, interface modules, signal modules, and accessories.

Spare parts and accessories for S7-300 modules

Lists S7-300 parts and accessories that can be ordered separately, including order numbers for bus connectors, front connectors, and cables.

Directive on handling Electrostatic-Sensitive Devices (ESD)

Explains the meaning of electrostatic-sensitive devices (ESD) and the precautions necessary when handling modules sensitive to electrostatic discharge.

Service & support

Information on obtaining technical support, service, and training from Siemens for Industry Automation products.

Safety-relevant symbols

Explains safety-related symbols for devices without and with Ex protection, including their meaning and installation notes.

List of abbreviations

Provides a comprehensive list of abbreviations used in the document and their corresponding explanations.