IC600CB525RR，IC600CB525RRIC600CB525RR
結(jié)合PLC的組成和結(jié)構(gòu)分析PLC的工作原理
結(jié)合PLC的組成和結(jié)構(gòu)分析PLC的工作原理更容易理解。PLC是采用周期循環(huán)掃描的工作方式，CPU連續(xù)執(zhí)行用戶程序和任務(wù)的循環(huán)序列稱為掃描。CPU對用戶程序的執(zhí)行過程是CPU的循環(huán)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(dāng)前值，然后寫到輸入映像寄存器區(qū)域。在之后的用戶程序執(zhí)行的過程中，CPU訪問輸入映像寄存器區(qū)域，而并非讀取輸入端口的狀態(tài)，輸入信號的變化并不會影響到輸入映像寄存器的狀態(tài)，通常要求輸入信號有足夠的脈沖寬度，才能被響應(yīng)。
（2）執(zhí)行程序階段。 用戶程序執(zhí)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(zhí)行直到最后一條指令結(jié)束，程序運行結(jié)果放入輸出映像寄存器區(qū)域。在此階段，允許對數(shù)字量I/O指令和不設(shè)置數(shù)字濾波的模擬量I/O指令進(jìn)行處理，在掃描周期的各個部分，均可對中斷事件進(jìn)行響應(yīng)。
（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(zhí)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(tài)。
（5）寫輸出階段。每個掃描周期的結(jié)尾，CPU把存在輸出映像寄存器中的數(shù)據(jù)輸出給數(shù)字量輸出端點（寫入輸出鎖存器中），更新輸出狀態(tài)。然后PLC進(jìn)入下一個循環(huán)周期，重新執(zhí)行輸入采樣階段，周而復(fù)始。
如果程序中使用了中斷，中斷事件出現(xiàn)，立即執(zhí)行中斷程序，中斷程序可以在掃描周期的任意點被執(zhí)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(yīng)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(yīng)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 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
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ALLEN BRADLEY 20AD8P0A0AYNNNNN 20AD8P0A0AYNNNNN
ALLEN BRADLEY 20AD3P4A3AYYAEG0 20AD3P4A3AYYAEG0
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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
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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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2706-B41J16 ALLEN BRADLEY MONITORS CRT REMANUFACTURED
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
