ISumCommand Interface

Interface for SumCommands (Combined commands)

Namespace: TwinCAT.Ads.SumCommand
Assembly: TwinCAT.Ads (in TwinCAT.Ads.dll) Version: 4.3.0.0

Syntax

C#

public interface ISumCommand

VB

Public Interface ISumCommand

The ISumCommand type exposes the following members.

Properties

	Name	Description
	Executed	Gets a value indicating whether this ISumCommand was already executed.
	Failed	Gets a value indicating whether this ISumCommand failed.
	Result	Gets teh AdsErrorCode of the main SumCommand ADS Request
	SubResults	Gets the sub results of the single Sub Requests.
	Succeeded	Gets a value indicating whether this ISumCommand is succeeded.

Remarks

ADS offers powerful and fast communication to exchange any kind of information. It's possible to read single variables or complete arrays and structures with each one single ADS-API call. The ADS Sum Command command offers to read with one singale ADS call multiple variables which are not structured within a linear memory. As a result the ADS caller application (like scada Systems etc.) can extremly speed up cyclic polling : Sample :

Until now : Polling 4000 single variables which are not in a linear area (like array / structure / fixed PLC address ) would cause 4000 single Ads-ReadReq with each 1-2 ms protocol time. As a result the scanning of these variables take 4000ms-8000ms.
New Ads-Command allows to read multiple variables with one single ADS-ReadReq : 4000 single variables are handled with e.g. 8 single Ads-ReadReq (each call requesting 500 variables) with each 1-2 ms protocol time. As a result the scanning of these variables take just few 10ms.

	REQUIREMENTS AND IMPORTANT LIMITATIONS ADS is just a transport layer, but there could be important side effects. So read this requirements and take care on limitations: Version of target ADS Device - ADS itself is just the transport layer, but the requested ADS device has to support the ADS-Command. Bytes length of requested data - Requesting a large list of values from variables is fine, but the requested data of the Ads-response (the data-byte-length) have to pass the AMS Router (size by default a 2048kb) So the caller has to limit the requested variables based on calculation of requested data-byte-length. Number of Sub-ADS calls : Highly recommended to max. 500 ! - If the PLC is processing one ADS request, it will completely work on this single ADS request BEFORE starting neyt PLC cycle. As a result one single ADS request with 200.000 sub-Ads-requests would cause that PLC would collect and copy 200.000 variables into one single ADS response, before starting next PLC. So this large number of ads-sub-commands will jitter the PLC execution ! We highly recommend to not request more than 500 Ads-Sub commands

Reference

TwinCAT.Ads.SumCommand Namespace

Further Information

ISumCommand Properties