l梯形图与助记符的对应关系：助记符指令与梯形图指令有严格的对应关系，而梯形图的连线又可把指令的顺序予以体现。一般讲，其顺序为：先输入，后输出（含其他处理）；先上，后下；先左，后右。有了梯形图就可将其翻译成助记符程序。上图的助记符程序为：
反之根据助记符，也可画出与其对应的梯形图。
l梯形图与电气原理图的关系：如果仅考虑逻辑控制，梯形图与电气原理图也可建立起一定的对应关系。如梯形图的输出（OUT）指令，对应于继电器的线圈，而输入指令（如LD，AND，OR）对应于接点，互锁指令（IL、ILC）可看成总开关，等等。这样，原有的继电控制逻辑，经转换即可变成梯形图，再进一步转换，即可变成语句表程序。
有了这个对应关系，用PLC程序代表继电逻辑是很容易的。这也是PLC技术对传统继电控制技术的继承。
程序设计在自动化系统的应用越来越广泛，例如plc与操作界面的数据交换，通过通讯对变频器的控制，plc的连网等等。
Omron E5BS-QHKJ Temperature Controller
Omron E2K-C25ME1 Adjustable Capacitive Switch (8)
Numatics R2 Series 2 & 3-Position 4-Way Valves
Novellus CMP 676 Polisher Ind. Computer SpeedFam MP2
Motorola NTN5196A 6-Unit Battery Charger Radius P100
Motorola MVME 946C Mainframe Chassis PLC Module Rack
Motorola MVME 2600-1 VME Mainframe Processor Board
Mizar MZ VME8400 Floppy Disk Controller Board VME MVME
Mizar MZ VME8210 512K Ram Board VME MVME
Mizar MZ VME8115 CPU Board VME MVME
Lightwave Comm Lantronix SAR6105 Shared-Access Router
Linear Instruments 156 Strip Chart Recorder
Lightwave Comm Lantronix Network Interface
ISCO Model 900 Delay Timer
Cisco PSA18U-480C AC Power Adapter BRAND NEW!!
Dickson THTrace THP7F Temp Humidity Chart Recorder
Hewlett Packard HP C7670A ScanJet Auto Document Feeder
Georg Fischer +GF+ 199.021.947 Diaphragm Valve 1/2″
Georg Fischer +GF+ 199.027.973 Diaphragm Valve 1″
Georg Fischer +GF+ 168.315.534 A Type 315 Valve 1″
Omron 3G8B2-Z8040 MA010 CS001 NI021 NO020 PS000 PLC Rac
Ohaus 6010 Moisture Determination Laboratory Balance
Motorola NLN766B 6-Unit Battery Charger
Mizar MZ VME8315 Real-Time Clock & SRAM Board VME MVME
Mizar MZ VME8305 PIO Board VME MVME
LKB 2089 Bromma Uvicord III Control & Detector Units
Linear Instruments 212 Single-Pen 10″ Chart Recorder
Linear Instruments 885 Versagraph Chart Recorder 2-CH
ISCO Power Supply Model 453
Human Designed Systems HDS ViewStation BA-G2500G2-101
HP J2552A/B JetDirect Print Server Ethernet & LocalTalk
Gilford Inst. Lab Inc. 2520F InVitro Diagnostic Column
Georg Fischer +GF+ 199.021.427 Diaphragm Valve 32mm
Georg Fischer +GF+ 175.315.534 Type 315 Valve 1″
Gordos PB-24SM 24-Pos Mounting Board w/ IDC5 ODC5 OAC5
Gordos PB-24SM 24-Pos Mounting Board w/ Crydom Relays
GLI AccuChlor Residual Chlorine System AC1000P1
Dell TrueMobile 2300 Wireless Broadband Router
InFocus Systems PanelBook 550 LCD Projection Panel
Black Box MX881A Async Sync Local Mux Multiplexer
Fujitsu FC9607AWA1 Alarm & Orderwire Unit FLM 2400 ADM
Fuji Film Fujica Single-8 Z1 Camera w/ Fujinon Lens
Fujitsu EA1550S EA1000 Telecom ATM Switch Mainframe
FPM Analytics 8200-110-030 Analytical Information Sys
Fluoroware Dymak 8PC-16F-01 Pneumatic Pinch Valve
Fisher Scientific Accumet15 Accumet 15 pH Meter
Festo CPV10-VI Solenoid Valve Terminal CPV10-VI-P4
Exor UniOP MDOOR-04-0045 HMI Display
Epson NB3s Laptop 640 kB Memory w/ Adapter
Entegris BV6-12F-01 Magnaflo Plug Valve NEW
Elmo EV-308 Visual Presenter with LU-308 Lighting Units
Dynamation 1031 Dynagaurd AutoCal Gas Detection Monitor
Digital M7606-AC M7606 KA630 PN: 5016523-01 CPU Board
DigiDesign PRO Tools Quad Audio Interface
Datel DVME-626 16-Bit Digital Analog VME VMEbus Board
Dataforth SCM9B-1352 R Thermocouple Module
FiberOptic Specialties LS86/110 150W Lite Source
Dataforth SCM5B30-03 Analog Voltage Input Module
AML M3000 Portable Bar Code Reader
Western Digital Winchester Floppy WD1003V-MM2 Disk Cont
