描述
除了执行用户程序外，在每次循环过程中，PLC还要完成内部处理、通信处理等工作，一次循环可分为5个阶段（见图1-5）。PLC的这种周而复始的循环工作方式称为扫描工作方式。由于计算机执行指令的速度极高，从外部输入-输出关系来看，处理过程似乎是同时完成的。
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NetApp 110-01599 PCI NVRAM Memory Board 32MB *NEW*
Intel 717040-004 Pro 1000 PCI Fiber Card – NetApp F880
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NetApp X1941A SP-1941A Cluster Cable Network Appliance
NETAPP 111-00058 DUAL FIBRE SERVER ADAPTER
NetApp 200-00641 Dual FN/W SCSI Controller Card
SEGATE ST3500630NS 500GB SATA HDD NetApp XYR 92557-01
Intel A06512-005 Pro 1000 Network Card from NetApp F880
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NETAPP 2GB ESH2 X5511A-R5 MODULE CONTROLLER DS14MK2
VR5VR567218FBPN1 2GB Net App
4x NetApp X274B-R5 108-00082 144GB FC 10K DS14 MK2 MK4
NetApp DS14MK2 W/ (5) 146GB 10K & (2) ESH2 Controllers
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