Autosync - ctNet Sync Master Redundancy

This function ensures that a CTNet Sync Master is always present on a CTNet token ring.

In order for cyclic data to be exchanged between nodes on a CTNet, one of the nodes must be set as CTNET Sync Master responsible for generating the Sync telegram. The reception of the Sync telgram by a node causes it to transmit cyclic data.

Every time the AUTOSYNC function block is called it monitors the CTNet token ring to ensure that a Sync Master is present. If a Sync Master cannot be detected and there is no other node running AUTOSYNC with a node address lower than the local node, the function block will automatically reconfigure the local node to become Sync Master and begin transmitting the Sync telegram.

Arguments

SRate% - range 0 to 25099

Specifies the cyclic rate to be used if the node becomes Sync master. Specified in the form SSSFF where FF = the fast cyclic rate in milliseconds and SSS is the slow cyclic rate as a multiple of the fast data rate.

If SRate% is 0, AUTOSYNC will still monitor the CTNet token ring but will not make an attempt to become Sync master.

Link%

This argument specifies the number of the cyclic link that is reserved for use by the AUTOSYNC block. the convention is that the reserved link is given the name AUTO_SYNC. See the Cyclic Data Configuration section below for more information.

Return Values

ARate%

Returns the cyclic data rate currently in use by the Sync Master node. This value has the same format as SRate%.

SNode%

The Returns the address of the Sync Master node.

Stat%

Stat% consists of a number of status bits. When set, the bits have the following meanings.

Cyclic Data Configuration

PLC registers _R79%, _S79% and one cyclic data link must be reserved for use with AUTOSYNC. The Cyclic Data Editor should be used to configure a link to broadcast _R79% to _S79%. The link should be given the name AUTO_SYNC in block capitals.

The link details should be set as follows.

Source Register	No.	Priority	Destination Register	Link Name
_R79%	0	Fast	_S79%	AUTO_SYNC

Defining the link in this way makes a name AUTO_SYNC_LINK available to the DPL program on the node. The name of this link should be passed as the value of the Link% parameter when AUTOSYNC is called. AUTOSYNC will then use the link to negotiate with other nodes on the CTNet network to determine which is Sync Master.

Example

This example shows use of the AUTOSYNC block on any module (UD75, MD29AN, SM-Applications). Note that the module setup parameters will also need to be used to set a CTNet node address..

Target/ Language Restrictions

This function is only supported on SM-Applications, UD75 and MD29AN. For UD75 and MD29AN, system file version 2.8.0 or later must be used.

Autosyncerror

This function block should be used in conjunction with the AUTOSYNC block to provide redundancy in the presence of a Sync Master on a CTNet token ring.

The AUTOSYNC block is responsible for dynamically making a node Sync Master if the existing Sync Master on a network stops generating the Sync telegram. To speed detection of the loss of the Sync Master on a network, the AUTOSYNCERROR block should be called whenever a run-time error occurs on a node.

Arguments

AUTO_SYNC_LINK

This is the ID of the fast cyclic link controlled by the AUTOSYNC block. This definition is created from the name given to the link assigned for use by AUTOSYNC using the Cyclic Data Editor.