| 摘要 |
A programmable controller of the type used to solve relay ladder diagrams is taught. The programmable controller includes a memory into which is placed a digital representation of the rungs of the ladder diagram. The dispositions of various switches and coils are periodically sampled by other portions of the programmable controller and stored in other memory locations. At appropriate times between sampling intervals, the various memory information are combined and provided to a relay line solver which comprises part of the programmable controller. The relay line solver updates the status of the relay ladder diagram and restores the updated information in a memory. This memory is used during the sampling intervals to change the status of output devices. The programming portion of the programmable controller includes UP, OPEN and RETURN keys which may be manipulated by an operator in an appropriate manner for entering the ladder diagram initially into the programmable controller memory or for updating or changing the status of the various rungs of the ladder diagram. The entry keys are such that contact interconnection information is entered into the memory at the same time and by the same keys that are utilized to enter the contact information. This means that no separate memory words are required for contact interconnection information in the appropriate memory of the programmable controller. Notwithstanding the aforementioned, very complex rungs of ladder diagrams may be entered using the three previously-mentioned keys.
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