IC600BF947RR，IC600BF947RR，IC600BF947RR
結合PLC的組成和結構分析PLC的工作原理
結合PLC的組成和結構分析PLC的工作原理更容易理解。PLC是采用周期循環掃描的工作方式，CPU連續執行用戶程序和任務的循環序列稱為掃描。CPU對用戶程序的執行過程是CPU的循環掃描，并用周期性地集中采樣、集中輸出的方式來完成的。一個掃描周期主要可分為：
（1）讀輸入階段。 每次掃描周期的開始，先讀取輸入點的當前值，然后寫到輸入映像寄存器區域。在之后的用戶程序執行的過程中，CPU訪問輸入映像寄存器區域，而并非讀取輸入端口的狀態，輸入信號的變化并不會影響到輸入映像寄存器的狀態，通常要求輸入信號有足夠的脈沖寬度，才能被響應。
（2）執行程序階段。 用戶程序執行階段，PLC按照梯形圖的順序，自左而右，自上而下的逐行掃描，在這一階段CPU從用戶程序的第一條指令開始執行直到最后一條指令結束，程序運行結果放入輸出映像寄存器區域。在此階段，允許對數字量I/O指令和不設置數字濾波的模擬量I/O指令進行處理，在掃描周期的各個部分，均可對中斷事件進行響應。
（3）處理通信請求階段。 是掃描周期的信息處理階段，CPU處理從通信端口接收到的信息。
（4）執行CPU自診斷測試階段。在此階段CPU檢查其硬件，用戶程序存儲器和所有I/O模塊的狀態。
（5）寫輸出階段。每個掃描周期的結尾，CPU把存在輸出映像寄存器中的數據輸出給數字量輸出端點（寫入輸出鎖存器中），更新輸出狀態。然后PLC進入下一個循環周期，重新執行輸入采樣階段，周而復始。
如果程序中使用了中斷，中斷事件出現，立即執行中斷程序，中斷程序可以在掃描周期的任意點被執行。
如果程序中使用了立即I/O指令，可以直接存取I/O點。用立即I/O指令讀輸入點值時，相應的輸入映像寄存器的值未被修改，用立即I/O指令寫輸出點值時，相應的輸出映像寄存器的值被修改。
ALLEN BRADLEY 2706-P42C 2706P42C
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ALLEN BRADLEY 2412B-A030DBD-7F-24J-41-98D 2412BA030DBD7F24
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ALLEN BRADLEY 22996-006-01 DIGITAL METERING SYSTEM 240/120V-AC 1/2-1/3HP D307559
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ALLEN BRADLEY 2100 SIZE 5 MOTOR STARTER 400 AMP BREAKER MCC BUCKET NO DOOR
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ALLEN BRADLEY 2100 15 AMP BREAKER 5 HP 480V AC DRIVE 1336 VFD MCC MCCB BUCKET
ALLEN BRADLEY 2100 1336t-b025-ax-gt1en 25HP AC DRIVE VFD MCC MCCB BUCKET
ALLEN BRADLEY 20AE3P9A0AYNNNNN POWER FLEX 70 SERIES A **
ALLEN BRADLEY 20AD8P0A0AYNNNNN 20AD8P0A0AYNNNNN
ALLEN BRADLEY 20AD3P4A3AYYAEG0 20AD3P4A3AYYAEG0
ALLEN BRADLEY 20AD3P4A3AYNNNNN 20AD3P4A3AYNNNNN
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Allen Bradley 194RNJ400P3 **GENUINE** 194RN J400P3
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Allen Bradley 1791-16AC Module 179116AC With Manual (Pack of 3) -
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ALLEN BRADLEY 1784-PCMC SER. B 1784-PCMK 1784-PCM5
ALLEN BRADLEY 1775-MR8 1775MR8
ALLEN BRADLEY 1775-MR8 MEMORY MODULE EXCELLENT CONDITION
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ALLEN BRADLEY 1756-MVID 1756MVID
ALLEN BRADLEY 1756-M14 -- 1756M14
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ALLEN BRADLEY 1746-NT4 1746NT4
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ALLEN BRADLEY 170024 170024
ALLEN BRADLEY 140G-J6F3-D25 140GJ6F3D25
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Allen Bradley 1398-DDM-030 /A Ultra 200 3000W Universal Drive 1PH 110/240V AC
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ALLEN BRADLEY 1326AB-A1G-11 1326ABA1G11
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AB Allen Bradley 8410-KYBD 8000KYBD 8000KYBS Keyboard Complete 8000XKBM
AB 512-CAB-6P-24R
2711E-K10C6 ALLEN BRADLEY PANELVIEW
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1336F-AQF50-AA-EN-HASP-L6E ALLEN BRADLEY DRIVES REMANUFACTURED
1305-BA09A ALLEN BRADLEY DRIVES REMANUFACTURED
1305-BA04A-HA2 ALLEN BRADLEY MOTOR CONTROLLER
* * Allen Bradley 1771-DE/B Series B Absolute Encoder Module
* * Allen Bradley 1394-DIM AC Servo Control
