| 摘要 |
A programmable controller (PLC) facilitates modifications to programs running therein, readily accommodates addition and removal of intelligent modules contained therein, and offers good maintenanceability. In the PLC a processing unit of an intelligent module is configured equivalent to a processing unit of a CPU module. Registers and memories of respective intelligent modules are allocated in a memory map of the CPU module to build a hardware configuration which allows the processing unit of the CPU module to read and write the registers and memories of the respective intelligent modules allowing the intelligent modules to be controlled similar to the CPU module. Software running on the CPU module is provided with instructions which indicate that it is executed in an intelligent module but can be processed either by the CPU module or the intelligent module.
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