描述
PLC采用循环扫描的工作方式，在PLC中用户程序按先后顺序存放，CPU从第一条指令开始执行程序，直到遇到结束符后又返回第一条，如此周而复始不断循环。PLC的扫描过程分为内部处理、通信操作、程序输入处理、程序执行、程序输出几个阶段。全过程扫描一次所需的时间称为扫描周期。当PLC处于停状态时，只进行内部处理和通信操作服务等内容。在PLC处于运行状态时，从内部处理、通信操作、程序输入、程序执行、程序输出，一直循环扫描工作。
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Reliance Electric 0-52841 PC Board Static Ratio 052841
New Reliance Cardpack Current Summing Card 0-49060-1
Reliance Cardpack Current REFERENCE Card 0-49060-3 NEW
Reliance Electric RE 3V2160 GV3000 VS Drive 3 HP NIB
RELIANCE VS VLDD O-51847-3
1.5 HP RELIANCE GEAR REDUCER WITH MOTOR DRIVE (3882)
Dodge/Reliance Gear Reducer with Motor 140SM3A #1
Dodge APG Gear Reducer Size 140SM3A
Dodge/Reliance Gear Reducer with Motor 140SM3A #2
Dodge APG Gear Reducer Size 140SM3A
Reliance Board Card 804.55.04AU0 8045504AU0 PSC/D NEW
Reliance Programmable Controller AutoMate 15 45C15D
Reliance Board 804.55.10BSR 8045510BSR PSC/D/E NEW
