TwinCAT 3 PLC Lib: Tc2_System

Overview

Not all those function blocks and functions that are often needed in PLC applications are standardized in IEC61131-3. The Tc2_System library contains such functions and function blocks for the TwinCAT system which do not belong to the standard scope of IEC61131-3, and which are therefore manufacturer-specific.

 

General function blocks

Name
Description
Random number generator
Critical sections should be made mutually exclusive
Switches the user LED to PCs and Émbedded PCs with BIOS API support
Determines the index of the current task
 
 

ADS function blocks

Name
Description
Reading data via ADS
Reading data via ADS and returning the number of read data bytes
Writing data via ADS
Reading and writing data via ADS
Writing data via ADS and returning the number of read data bytes
Read the state of a device via ADS
Write control words to a device via ADS
Read device information via ADS
 
 

Expanded ADS function blocks

Name
Description
ADSREAD Indication
ADSWRITE Indication
ADSRDWRT Indication
ADSREAD Response
ADSWRITE Response
ADSRDWRT Response
 
 

Function blocks for data access

The function blocks can be used to process files from the PLC locally on the PC. The TwinCAT target system is identified by the AMS network address. This mechanism makes it possible, amongst other things, to store or to edit files on other TwinCAT systems in the network. Access to files consists of three sequential phases:

1.
Opening the file.
2.
Read or write access to the opened file.
3.
Closing the file.

Opening the file has the purpose of establishing a temporary connection between the external file, whose name is all that initially is known, and the running program. Closing the file has the purpose of indicating the end of the processing and placing it in a defined output state for processing by other programs.

Name
Description
Check the end of file
Open a file
Close a file
Get string from a file
Put string to a file
Read from a file
Write to a file
Move the file pointer
Get the file pointer position
Delete a file
Rename a file
Create new directory
Remove directory
 
 

EventLogger function blocks

The TwinCAT EventLogger has the task of managing all messages (events) appearing in the TwinCAT system; to forward them and where necessary to write them into the TwinCAT log file.

Name
Description
Sending and acknowledging TwinCAT EventLogger messages
Sending and acknowledging TwinCAT EventLogger messages
Sending and acknowledging TwinCAT EventLogger messages
 
 

IEC steps / SFC flags function blocks

These functions / function blocks are required if IEC steps or SFC flags are used in SFC programs/projects.

Name
Description
Required if SFC flags are used
Required if SFC flags are used
Required if SFC flags are used
Required if SFC flags are used in order to format strings with error description
Enables the use of IEC steps
 
 

Watchdog function blocks

Name
Description
Activates or deactivates the PC watchdog
Only available on IPCs with the following mainboards: IP-4GVI63, CB1050, CB2050, CB3050, CB1051, CB2051, CB3051
Activates or deactivates the PC watchdog
Only available on IPCs with the following mainboards: CBxx63 with a BIOS version >=0.44
 
 

Time function blocks

Name
Description
Read the CPU cycle counter
Read the PLC task cycle counter
 
 

General functions

Name
Description
Returns information about the memory area in which the requested variable with the specified size is located
Compares an existing library with the required version
Converts individual IPv4 address bytes to a string
Converts an IPv4 address string to individual address bytes
Returns the object ID of the partner side of the mapping
Returns the current mapping status of a PLC variable
Reads information about the memory alignment used
Splits the path name into four individual components
Sets a bit in a DWORD
Setting/resetting of a bit in a DWORD
Reads a bit from a DWORD
Clears a bit in a DWORD
Determining the task index
Outputs a signal on one of the parallel port pins
Setting and checking a flag without option to interrupt it
 
 

ADS functions

Functions are described below which, with the aid of the ADS interface makes some of the functions of the Windows-NT operating system (such as the output of message boxes) accessible through PLC calls.

Name
Description
Log a DINT variable into NT Eventlog and/or Messagebox
Log a (L)REAL variable into NT Eventlog and/or Messagebox
Log a STRING variable into NT Eventlog and/or Messagebox
Creates AmsNetId string
Converts AmsNetId string to array of address bytes
 
 

Character functions

Name
Description
Converts string character to ASCII number
Converts ASCII number to string character
 
 

I/O port access

Name
Description
Reads from I/O Port
Writes to I/O Port
 
 

Memory functions

Number of functions, which provide direct access to memory areas in the PLC runtime system.

 
Note
System crash or access to forbidden memory areas
The fact that these functions allow direct access to the physical memory means that special care is called for in applying them! Incorrect parameter values can result in a system crash, or in access to forbidden memory areas.
Name
Description
Compares the values of variables in two memory areas
Copies the values of variables from one memory area to another
Copies the values from overlapping memory areas
Sets the variables in a memory area to a particular value
 
 

Time functions

Name
Description
Read the operating system time stamp
Read the target start time of the task