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。
要想实现plc的通讯编程，首先所选的plc必须有强大的通讯能力，就是说plc的操作系统能够支持多种通讯格式，通常一种品牌的plc如果能够提供给用户更多的编程自由度，那么这种品牌的技术开发能力就越强大，大多数品牌只能提供固定格式的通讯格式或协议，这就大大局限了plc与其他智能设备的数据交换。
我们的plc产品具有RS232和光电隔离的RS485两个自由通讯口,两个通讯口可以同时收发数据，几乎可以适应所有通讯格式，可以提供CRC和BCC等多种校验方式。
以一台PLC通过485通讯控制多个某品牌的变频器为例：
CIMR F7U20P7 Yaskawa SERIES Varispeed Drive 1HP, 230V
Yaskawa ServoPack Servo Drive CACR-HR20BB
YASKAWA YASNAC CIMR MT III 7.5K SPINDLE DRIVE
YASKAWA CIMR-MTIII-7.5K SPINDLE DRIVE NIB FREE SHIP
Yaskawa Varispeed 505 MT Spindle Drive CDMR-MR-11K MORI
Yaskawa CACR-SR15BE12G Servo Drive
YASKAWA VARISPEED 505 SPINDLE DRIVE CDMR-ZII JPDC-C036
YASKAWA INVERTER MOTOR SPEED CONTROLLER FREQUENCY DRIVE
YASKAWA SGDB-60ADSY44 SERVOPACK SERVO DRIVE 8HP 40A*NIB
YASKAWA CACR-SR44BC1CSY349 SERVOPACK SERVO DRIVE *XLNT*
YASKAWA CACR-SR30BC1AFY244 SERVOPACK SERVO DRIVE *XLNT*
SGDA-05ASY195 Yaskawa AC ServoPack SIGMA I Servo Drive
One-day shipping available
SGDA-08AS Yaskawa AC ServoPack SIGMA I Servo Drive Unit
One-day shipping available
Yaskawa / Magnetek GPD515C-A049 15HP 230V AC Drive
One-day shipping available
CACR-HR30BB YASKAWA SERVOPAK/DRIVE
One-day shipping available
CACR-PR20BC3AMY78 Yaskawa Yasnac AC Servo Drive ServoPa
One-day shipping available
JPDC-C024 ETC003420 Yaskawa Spindle Drive Control PCB
One-day shipping available
CACR-IR15SEB Yaskawa Motoman AC Servo Drive ServoPack
One-day shipping available
CACR-IR15SB Yaskawa Motoman AC Servo Drive ServoPack
One-day shipping available
CACR-IR15SFB Yaskawa Motoman AC Servo Drive ServoPack
One-day shipping available
YASKAWA USASEM SERVO MOTOR & DRIVE 3.51kW 27.4A 1500RPM
Yaskawa Drive Servopack CACR-SR30BE12G CACRSR30BE12G-E
YASKAWA SERVOPACK DRIVE CACR-SR 15BB1BF CACR-SR15BB1BF
YASKAWA CIMR-F7U2011 DRIVE 240V 45A ***RFB***
CACR-PR15BC3AM-Y812 Yaskawa Yasnac AC Servo Drive Servo
One-day shipping available
Yaskawa / Magnetek CIMR-G5M47P5 15HP 460V AC Drive
One-day shipping available
Yaskawa / Magnetek CIMR-P5M4022 40HP 460V AC Drive P5
One-day shipping available
YASKAWA VARISPEED DRIVE 626MTII CIMR-MTII-11K *w/ video
SGDA-04AS Yaskawa AC ServoPack SIGMA I Servo Drive Unit
One-day shipping available
CIMR-22CS2 Yaskawa Juspeed-F Inverter AC Drive 200-230V
One-day shipping available
Yaskawa / Magnetek CIMR-P5M2018 30HP 230V AC Drive
One-day shipping available
CACR-SR10SZ1SFY90 Yaskawa Yasnac AC Servo Drive ServoPa
One-day shipping available
CACR-SR10BB1AF Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-PR10BC3CS-Y10 Yaskawa Yasnac AC Servo Drive ServoP
One-day shipping available
CACR-SR10SB1BF Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-SR10SB1AFY100 Yaskawa Yasnac AC Servo Drive ServoP
One-day shipping available
CACR-SR10BY1SF-E Yaskawa Yasnac AC Servo Drive ServoPac
One-day shipping available
CACR-SR10SB1AF Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-SR10BY1SFY18 Yaskawa Yasnac AC Servo Drive ServoPa
One-day shipping available
CACR-SR10BC1ESY262 Yaskawa Yasnac AC Servo Drive ServoP
One-day shipping available
CACR-SR10SZ1SFY221 Yaskawa Yasnac AC Servo Drive ServoP
One-day shipping available
CACR-SR10SZ1SSY217 Yaskawa Yasnac AC Servo Drive ServoP
One-day shipping available
CACR-SR10SZ1SSY86 Yaskawa Yasnac AC Servo Drive ServoPa
One-day shipping available
CACR-HR15BBY81 Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
SGDB-20ADGY60 Yaskawa AC ServoPack SIGMA I Servo Drive
One-day shipping available
CACR-HR15BB Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-HR10UBY9 Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-HR10BB Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-HR10BABY5 Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
SGDB-20ADG-P Yaskawa AC ServoPack SIGMA I Servo Drive
One-day shipping available
CACR-IR10SB Yaskawa Motoman AC Servo Drive ServoPack
One-day shipping available
CACR-IR10SC1 Yaskawa Motoman AC Servo Drive ServoPack
One-day shipping available
YASKAWA JUSP-ACP15GA DRIVE PACK CONVERTER UNIT
YASKAWA CACR-SR03BC1KS-Y264 SERVOPACK SERVO DRIVE*XLNT*
Yaskawa / Magnetek CIMR-G3U2015 20HP 230V AC Drive G3
One-day shipping available
Yaskawa / Magnetek CIMR-G3U2018 25HP 230V AC Drive G3
One-day shipping available
CACR-SRA5AB2ERY19 Yaskawa Yasnac AC Servo Drive ServoPa
One-day shipping available
Yaskawa / Magnetek CIMR-P5M4018 30HP 460V AC Drive
One-day shipping available
SGDB-30ADG Yaskawa AC ServoPack SIGMA I Servo Drive
One-day shipping available
CACR-SR05AC1ESY105 Yaskawa Yasnac AC Servo Drive ServoP
One-day shipping available
CACR-SR05AB1ER Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-SR05AA2AH Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-SR05AC1ER Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-SR05BB1AFY114 Yaskawa Yasnac AC Servo Drive ServoP
One-day shipping available
CACR-SR05BB1AF Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-SR05BY1SG-E Yaskawa Yasnac AC Servo Drive ServoPac
One-day shipping available
CACR-SR05SB1AFY114 Yaskawa Yasnac AC Servo Drive ServoP
One-day shipping available
CACR-SR05BE13SY44 Yaskawa Yasnac AC Servo Drive ServoPa
One-day shipping available
CACR-SR05BE12G-E Yaskawa Yasnac AC Servo Drive ServoPac
One-day shipping available
CACR-SR05BB1BF Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-SR05SB1AF Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-SR05BC1ES-Y278 Yaskawa Yasnac AC Servo Drive Servo
One-day shipping available
CACR-SR05SB1AFY187 Yaskawa Yasnac AC Servo Drive ServoP
One-day shipping available
CACR-SR05BC1CS-Y159 Yaskawa Yasnac AC Servo Drive Servo
One-day shipping available
YASKAWA SERVO MOTOR DRIVE- CACR-HR10BB NIB CACRHR10BB
One-day shipping available
YASKAWA YASNAC CIMR MT II 7.5K SPINDLE DRIVE
Yaskawa Varispeed 626VM3 Spindle Drive CIMR-VMS20110-PX
Yaskawa Yasnac CACR-SR44SB1AFY307 AC Servo Drive Servo
CACR-HR05BAB11 Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-SR03SZ1SSY106 Yaskawa AC Servo Drive Unit
One-day shipping available
CACR-SR03SZ1SSY223 Yaskawa Yasnac AC Servo Drive ServoP
One-day shipping available
CACR-SR03SZ1SSY84 Yaskawa Yasnac AC Servo Drive ServoPa
One-day shipping available
CACR-SR03AB2ER Yaskawa Yasnac AC Servo Drive ServoPack
One-day shipping available
CACR-SR03SZ1SSY215 Yaskawa Yasnac AC Servo Drive ServoP
One-day shipping available
