Writing Variables - Siemens S7-1200 System Manual

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11.6 User-defined Web pages

Writing variables

User-defined pages can write data to the CPU. This is accomplished by using an AWP

command to identify a variable in the CPU to be writable from the HTML page. The variable

must be specified by PLC tag name or data block tag name. You can declare multiple

variable names in one statement. To write the data to the CPU, you use standard HTTP

POST commands.

A typical usage is to design a form in your HTML page with text input fields or select list

choices that correspond to writable CPU variables. As with all user-defined pages, you then

generate the blocks from STEP 7 such that they are included in your STEP 7 program.

When a user with privileges to modify variables subsequently accesses this page and types

data into the input fields or selects a choice from a select list, the Web server converts the

input to the appropriate data type for the variable, and writes the value to the variable in the

CPU. Note that the name clause for HTML input fields and HTML select lists uses syntax

typical for the name clause of the AWP_In_Variable command. Typically enclose the name in

single quotation marks and if you reference a data block, enclose the data block name in

double quotation marks.

For form management details, refer to documentation for HTML.

For both Name clauses and Use clauses, the complete name must be enclosed in single

quotation marks. Within the single quotes, use double quotation marks around a PLC tag

and double quotation marks around a data block name. The data block name is within the

double quotes but not the data block tag name. Note that for data block tags, you use the

name of the block and not a data block number.

If no Use clause is provided, Varname1 is the variable to be written. It can be a

PLC tag name from your STEP 7 program or a tag from a specific data block.

If a Use clause is provided, Varname1 is an alternate name for the variable

referenced in <Varname2> (Page 634). It is a local name within the HTML page.

If a Use clause is provided, Varname2 is the variable to be written. It can be a PLC

tag name from your STEP 7 program or a tag from a specific data block.

S7-1200 Programmable controller

System Manual, 03/2014, A5E02486680-AG