Writing A Special Variable; Reference: Html Listing Of Remote Wind Turbine Monitor Web Page - Siemens S7-1200 System Manual

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11.6 User-defined Web pages

Note that if a user-defined page has a data entry field for a writable data block tag that is a

string data type, the user must enclose the string in single quotation marks when entering

the string value in the field.

Note that if you declare an entire data block in an AWP_In_Variable declaration such as <!--

AWP_In_Variable Name='"Data_block_1"' -->, then every tag within that data block can be

written from the user-defined Web page. Use this when you intend for all of the tags in a data

block to be writable. Otherwise, if you only want specific data block tags to be writable from

the user-defined Web page, declare it specifically with a declaration such as <!--

AWP_In_Variable Name='"Data_block_1".Braking' -->

Writing a special variable

The "Remote Wind Turbine Monitor" Web page writes the special variable

SERVER:current_user_id to a PLC tag in the CPU, providing that the user has modify

privileges. In this case, the PLC tag value contains the user ID of the user who is accessing

the "Remote Wind Turbine Monitor" Web page.

The Web page writes the special variable to the PLC and requires no user interface.

Sample HTML code

Wind_turbine.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"

"http://www.w3.org/TR/html4/loose.dtd">

This test program simulates a Web page to monitor and control a Wind

Required PLC tags and Data Block Tags in STEP 7:

User_ID: Int

Data Blocks:

Data_block_1

Tags in Data_Block_1:

TurbineNumber: Int

WindSpeed: Real

WindDirection: Real

S7-1200 Programmable controller

System Manual, 03/2014, A5E02486680-AG