在PLC进入运行状态后，从存储器中逐条读取用户程序，经过命令解释后按指令规定的任务，产生相应的信号，去启闭有关控制门电路。分时分渠道地去执行数据的存取、传送、组合、比较和变换等操作，完成用户程序中规定的逻辑式算术运算等任务。根据运算结果，更新有关标志位的状态和输出映象寄存器的内容，再由输出映象寄存器的位状态式数据寄存器的有关内容，实现输出控制、制表、打印式数据通讯等。
PLC常用的CPU主要采用通用微处理器、单片机或双极型位片式微处理器。通用的微处理器常用的是8位机和16位机，如Z80A、8085、8086、6502、M6800、M6809、M68000等。单片机常用的有8039、8049、8031、8051等。双极型位片式微处理器常用的有AMD2900、AMD2903等。
Reynolds Double Offset Link 2-1/2" Pitch 200-2
co 41 Carbon Steel Globe Valve 28T-FS2 1/2'' NPT Class 800 Psi Free Shipping
United Electric Controls Pressure Switch J
Foxboro Temperature Probe PR-14BBI-018
WEG Electric Motor 30HP 575V (22kW)
Actek Metric Swivel Hoist Ring Long U-Bar 47142
Westinghouse Control realy BFD55S 275A288G01
Link-Belt Adaptor Sleeve SNW 4-15/6"
man-Milliken Plug Valve 6" VPAPF1 / 171M
GE Contactor CR353EH3BA1
Rosemount Pressure Transmitter C115 1GP8E112S1M1B3E6
Thomas & Betts Connecting Splice Plate SHW3SSP (12)
Sherwood / W & T Chlorine Valve CGA 820
Mar-Bal Electric Insulator 5250-A5 (Lot of 10)
Siemens Digital Input Module 6ES5 430-7LA11
Link-Belt Seal Ring LB68393R 2-7/16"
Allen-Bradley Isolated Pilot Duty Module 1771-OD16/B
SenTech Digital Stand-aloneTransmitter CT200
Turck Minifast Cordsets RKF 66-1M (5)
MTS Temposonics Linear-Position Sensor Type RPV Free 1 Year Warranty
Dayco Power Wedge Cog Belt 5VX1000
Mac-Weld Thermowell 6" TW03A12L07.5
3R Industries Teadit Graflex Gasket 7-1/2" Dia. (7 Pcs)
Broyce Controls Time Delay Relay B8DD0
Allen-Bradley Isolated Analog Input Module 1771-IL
Square D Fusible Panelboard QMB364W
Samson Seal Gasket 6" (Lot of 2)
Schneider Telemecanique Ram Cartridge 64K TSX RAM 64 16
Hammond Transformer PH50JG (Lot of 2)
RPS ABCO Fiberglass FRP Flange 1"
Browning Gripnotch Belt Cogged V Belt AX47 (Lot of 2)
Ametek / Wika Pressure Gauge w/ Diaphragm 0-400 kPa
Square D Current Transformer 64R-201 (lot of 3)
Reliance Electric A/B Interface Module 57418-E
梯形图语言的编程元件的符号和表达方式与继电器控制电路原理图相当接近。
