Section 3 Features
Attributes
28
1MRS755221
3.2 Attributes
In addition to item tags for process data (indications and commands), the SPA OPC
Server also provides some item tags for controlling the devices and retrieving status
information from them. These item tags are called attributes.
There are three categories of attributes: server attributes, line attributes and device
attributes. These attributes are described in sections 3.2.1, 3.2.2 and 3.2.3.
Table 3-1: Namespace legend
SPA OPC Server
An object representing the SPA OPC Server
.
SPA Line
An object representing a physical communication line (=serial port). You can
define up to 8 lines per OPC server.
SPA Device
An object representing a physical device. You should not have more than 30
devices/modules per line or more than 200 devices/modules per server.
SPA Rack
Collection of SPA Modules in one physical rack.
SPA Module
A SPA Device placed in a relay rack, for example, SPACOM modules. You
should not have more than 30 modules/devices per line or more than 200
modules/devices per server.
SPA Signals
An OPC item tag/node representing a signal, usually a command or an
indication. There are seven types of signals, see
on page 44. Signals describe the actual information that a device or module
provides. To view the icons of all the signals, see Table 4-1.
Attributes
A predefined node that contains item tags for controlling or retrieving status
information for the parent node. The parent node can be the server, a line or
device.
