描述
在用户程序执行阶段，可编程逻辑控制器总是按由上而下的顺序依次地扫描用户程序(梯形图)。在扫描每一条梯形图时，又总是先扫描梯形图左边的由各触点构成的控制线路，并按先左后右、先上后下的顺序对由触点构成的控制线路进行逻辑运算，然后根据逻辑运算的结果，刷新该逻辑线圈在系统RAM存储区中对应位的状态；或者刷新该输出线圈在I/O映象区中对应位的状态；或者确定是否要执行该梯形图所规定的特殊功能指令。
MICROSCAN USB MS-Q Quadrus DPM 1D 2D barcode reader
Dade Behring MicroScan Auto Scan 4 Invitro Diagnostic
Microscan MS-820 Industrial Barcode Scanner w/Interface
Tracor Northern / Noran Instruments 5525 Microscan
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Microscan Barcode Scanner Lot MS-710 VS-310 MS-3 Laser
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Microscan Mdl. FIS-0710-005 Scanner, MS-710 Series
Baxter Microscan Walkaway-40 Blood Culture Analyzer
