ADS Indication/Response

The ADS Indication/Response function blocks enable the establishment of a client-server communication between an ADS device and a PLC task of a bus controller or between two bus controllers (e.g. BC9000).  The ADS device can be, for example, a Windows application (uses the AdsDLL/AdsOcx) or another PLC runtime system.  Communication between the ADS device and the PLC task is processed using the following service primitives:

• Request     
• Indication
• Response 
• Confirmation

The communication between an ADS device and a PLC task has the following sequence: an ADS device sends a request to the target device (PLC task). This request is registered in the target device by an indication. The target device (PLC task) thereupon carries out a corresponding service. The service to be carried out is encoded via the index-group/offset parameter. Next the PLC sends a response to the ADS device.  The response is registered as confirmation by the ADS source device.
Only one instance of the indication and response function block can meaningfully be used per PLC task. Corresponding with the available ADS services: READ, WRITE and READ & WRITE there is an appropriate indication or response function block for each service. 

The ADS devices are addressed via a port address ( PORT ) and a network address (NETID). 

Example:

The PLC task of a BC9000 Bus Controller with the network address "172.64.23.12.1.1" is to be addressed. The PLC task of the Bus Controller has the port number: 800.

The network address:
PORT = 800
NETID = '172.64.23.12.1.1'

Comments:

• In order for a request to be forwarded to the PLC task, the most significant bit must be set in the IndexGroup parameter during the request, e.g. IG:=0x80000001.
• The maximum data size that a BC9xxx Bus Controller can send ( e.g. with ADSREADRESBC ) and receive ( e.g. with ADSWRITEIND ) is limited to 1980 bytes.

Requirements