Function blocks for data synchronization

Available with AXC F 2152 and AXC F 3152

General concept

At the Applicative System Redundancy, the same application program is in operation on the two redundant PLCs (First PLC and Second PLC) but only one PLC (either First or Second) controls the process. By means of the ASR_ContrRed_2152 or the ASR_ContrRed_3152 function block the PLCs negotiate among themselves who controls the process. The PLC, which controls the process is the Primary, the other PLC has the role of the Backup. 

The task of the function blocks described here is to synchronize values of selected variables between the PLCs. The library provides function blocks for common standard data types. For this purpose, there are two different types of function blocks:

• Main function block for establishing the communication link between the PLCs
• Function blocks for the synchronization of standard data types

Prerequisites

From the PLCnext Store, download the ASR AXC F 2152 or the ASR AXC F 3152 function block library (free of charge) and import it into PLCnext Engineer on your computer.

Main function block ASR_DataSync

The input parameters iRole,strOwnIP and strPartnerIP must be connected to the corresponding output parameters of the ASR_ContrRed_2152 or the ASR_ContrRed_3152 function block. Via the xUDP_SocketsActive output parameter, the function block indicates whether the UDP/IP sockets, necessary for the data synchronization, were successfully opened.

The xDataStructureConsistent output parameter indicates with a TRUE that the number and the sequence of calls of the function blocks for the synchronization of the standard data types are identical on both PLCs. Only if this bit indicates TRUE, the variables between the two controllers will be synchronized. Via the xOperatingState output parameter it is shown whether the communication between the two PLCs is in operation.

The iUsedBytes output parameter shows the number of bytes that are necessary for the synchronization of the variables (standard data types). The system supports a maximum of 32767 bytes for the data synchronization of standard data types.

The data exchange between the individual function blocks for the data synchronization is done by the means of the udtSyncData in-/out-parameter. Therefore, at each individual function block the same variable must be applied to this parameter.

Description of inputs and outputs

Name	Data type	Data direction	Description
iRole	INT	Input	Current role of the PLC: 0: Undefined 1: Primary 2: Backup
strOwnIP	STRING	Input	Own IP address. The proper syntax for this String is: ‘/IP=www.xxx.yyy.zzz’ (e.g. ‘/IP=192.168.0.91’)
strPartnerIP	STRING	Input	IP address of the Partner-PLC. The proper syntax for this String is: ‘/IP=www.xxx.yyy.zzz’ (e.g. ‘/IP=192.168.0.92’)
xUDP_SocketsActive	BOOL	Output	TRUE indicates that the UDP/IP sockets were successfully opened.
xDataStructureConsistent	BOOL	Output	TRUE indicates that the sequential arrangement of the function blocks for the standard data types is identical on both PLCs.
iUsedBytes	INT	Output	Number of used bytes for the data exchange of the standard data types.
xOperatingState	BOOL	Output	TRUE indicates that the data exchange of the standard data types is in operation.
udtSyncData	ASR_UDT_ ‎SYNC_DATA	In/Out	Parameter for the data exchange with the data type specific function blocks.

Function blocks for standard data types ASR_Data_*

By the means of these function blocks values of variables of standard data types can be synchronized between the PLCs. For this purpose, the active PLC (Primary) sends the values of the variables, which are applied to the...Value IN/OUT parameter, to the passive PLC (Backup). The passive PLC receives these values and copies them to the variables connected to the IN/OUT parameter.

‘*' is a placeholder for the supported data types. The function block is available for the data types BOOL, BYTE, WORD, DWORD, SINT, INT, DINT, UDINT, UINT, USINT, REAL, and LREAL.

Example for the WORD data type:

The variable which should be synchronized between the PLCs has to be applied to the...Value IN/OUT parameter.

Via the udtSyncData IN/OUT parameter the function block is connected to the responding ASR_DataSync main function block.

Description of inputs and outputs

Name	Data type	Data direction	Description
...Value	BOOL, BYTE, WORD, DWORD,  SINT, INT, DINT, USINT, UINT, UDINT, REAL, LREAL	IN/OUT	Variable which should be synchronized.
udtSyncData	ASR_UDT_ SYNC_DATA	IN/OUT	Parameter for the data exchange with the ASR_DataSync function block.