Controlling process for a controlling apparatus having a CPU and special function units

摘要

A method for controlling a control apparatus such as a programmable controller which includes a CPU and special function modules. The CPU conducts sequence control and the special function modules perform control other than sequence control in accordance with commands from the CPU. Each instruction represents a normal or special instruction. Special instructions include a first symbol denoting a special function unit-corresponding instruction and a second symbol denotes a special function type (independent of memory addresses). Once the CPU identifies a special function instruction by identifying the first symbol, the CPU stores the contents of the instruction step into a multi-directional access memory of the special function unit. Thereafter, in one embodiment, the CPU generates an interrupt requesting the special function unit to execute this instruction. In other embodiments, the CPU performs instruction processing to ensure, for example, that the instruction is a correct one for the selected special function module. The special function unit decodes and executes the instruction based upon the second symbol denoting the special function type.