Characteristics of the Saia PCD® Classic controllers
There are some special features and characteristics of the Saia PCD® Classic controllers to be mentioned. The list below tries to give an overview especially for people that already worked with a PLC of any kind:
No process image is used
No process image is generated. The I/Os are accessed right at the moment when the user program reads/writes an I/O. This behaviour was integrated in order to allow more spontaneous and therefore faster communication between the CPU and the I/Os and to reduce internal data transfer.
Integrated Web Server
Newer classic PCD types (introduced after 2000, e.g. PCD2.M170, PCD2.M480, PCD3.Mxxxx, PCS1) do have an integrated Web Server (no extra costs) in the Firmware (FW). To access the Web server the software Web Connect is needed and to generate project containing a PCD internal Web server the Web Builder is required. Both tools are part of the Controls Suite.
S-Bus as communication protocol
The SBC S-Bus is an integral component of the Firmware. Many other protocols are supported through special drivers (e.g. FBoxes).
Communication modules do not require additional space
Communication interfaces are directly mounted onto the main print of a CPU and therefore do not require additional space. A PCD2.M480 may handle up to 8 serial interfaces.
Communication modules are equipped with a co-processor
For a communication with high baud rates special communication modules containing a co-processor are available.
Predefined onboard data points
Saia PCD® Classic controllers do have predefined onboard medias (Flags as bit information and registers for 32 bit values). These medias are statically allocated in special onboard RAM and therefore do have a unique address. The format of the registers may be integer of floating point (Motorola fast floating point, conversion to IEEE is supported) or user defined.
I/O points are addresses by its physical location
All I/Os are addressed statically on the internal I/O bus. Therefore the addresses of mounted I/O modules is depending on its physical location. Each module has a I/O range of 16 digital I/Os (also if only 8 I/Os are physically present). Every module slot does have a unique base address.
Analogue I/O points are accessed by provided function blocks
Analogue I/Os, fast counting modules as well as motion control modules are accessed via a function block (FB, written in instruction language IL) or an FBox (graphically programmed with the Fupla Editor). These FB's and FBoxes are delivered together with the programming tool PG5 which is part of the Controls Suite.
Saia PCD® Controls Suite contains all tools for programming a Saia PCD® Classic
All Classic PCD's are to be programmed with the programming tool PG5 which is part of the Saia PG5® Controls Suite. Please refer to the programming introduction for more details.
