The PLC Command,I/O address,internal relay resource,the structure of the software,edits modules,memory frame and execution cycle are described in detail.

• 从规划PLC的控制命令、I/O地址、内部寄存器资源开始展开论述,并结合软件结构,说明了PLC的编辑和存储结构、循环扫描执行等模块。