Applications Programming Interface is abbreviated API. This option is to use 3rd Party Software as the interface to the field device. The API software package is installed on the SCADA node. The hardware manufacturer usually supplies the API software. Many proprietary network cards require the user to install software on the SCADA node PC in order to communicate with the automation devices on their proprietary network. The Siemens S7 interface is an example; it requires the SIMATIC NET software. The WebAccess driver communicates with the SIMATIC NET software. Allen-Bradley RS-LINX is another example, the WebAccess PLC5 driver communicates with RS-LINX software to access data from PLCs on Control Net. The Omron Host Link driver is another example of an API type interface.
The connection from the SCADA node to the PLC or automation device may be a Serial Port, TCP/IP or proprietary network card. Hence, it is possible to have a Serial connection to the device, but use the API Port type in WebAccess.
For More information on API type Com Ports see API Comport Properties.
To modify an existing Device, Select Device Properties.
Add your device to the API Port, by
selecting the API Port you have configured, then select Add
Device. The Configure Device Properties Page appears.
Figure 3-9Siemens S7 PLC Device uses SIMATIC NET software API
Figure 3-10SNMP Device uses Microsoft's "Simple Network Management Protocol"
Device Name is any user defined name. See Device Name for more information.
Description is a user defined. See Description for more information.
Unit Number, for most API interfaces, this is a "virtual number" and does not correspond to the actual Unit Number used in the protocol addressing. See Unit Number for more information.
The Device Type lists available Device Drivers for an API type Comport (e.g. Siemens S7, SNMP). See Device Type for more information. If your device Type does not appear, you may have configured the wrong Com Port type.
Notice that the Field changes depending on the Device Type selected from the pull down list.
bwDDE:
bwSNMP: IP, Community
SiemS7: Device, VFD, and CP Name
See the Device Driver Guide for you device type for detailed information.