Page 690 - Mechanical Engineers' Handbook (Volume 2)

1 Characteristics of General-Purpose Control Devices 681

Depending on the complexity of the control program and the degree of reprogramma-
bility required, GPCD programming may be supported by any of several means, including:
• An integral programming panel on the GPCD
• Portable programming and debugging tools
• Minicomputers, personal computers, or engineering workstations that may or may not
be connected to the GPCD during control operation
• An online computer system, for example, the area or cell controller shown in Fig. 2.

1.3 Device Architecture
Figure 3 illustrates a GPCD architecture capable of providing the required functional char-
acteristics:
• The memory provides storage for the programs and data entered into the system via
the communications processor.
• The control processor performs control actions under the direction of the stored pro-
gram as well as coordinates the operation of the other functions.
• The communications processor provides the means of accepting commands from and
providing status information to the supervisory system and operator’s console, inter-
changing status information with other GPCDs, and interacting with program devel-
opment and configuration tools.

Figure 3 Typical architecture of a GPCD.