3BSE031108R100 ABB

In order to complete the control strategy,in order to replace the relay and enable users to complete the control system ladder diagram similar to the relay circuit,a set of control algorithm function blocks(or subroutines),called the command system,are compiled,which are solidified in the memory ROM.It can be called by the user when programming an application.The instruction system can be roughly divided into two categories,namely basic instructions and extended instructions.The instruction system of subdivided general PLC includes:basic instruction,timer/counter instruction,shift instruction,transfer instruction,comparison instruction,conversion instruction,BCD operation instruction,binary operation instruction,increment/decrement instruction,logical operation instruction,Special operation instructions,etc.,these instructions are mostly similar to assembly language.In addition,PLC has also improved sufficient internal resources such as timers,counters,internal relays,registers and storage areas,which brings great convenience to programming.

为了完成控制策略，为了替代继电器，使用户等完成类似继电器线路的控制系统梯形图，而编制了一套控制算法功能块(或子程序)，称为指令系统，固化在存贮器ROM中，用户在编制应用程序时可以调用。指令系统大致可以分为两类，即基本指令和扩展指令。细分一般PLC的指令系统有:基本指令、定时器/计数器指令、移位指令、传送指令、比较指令、转换指令、BCD运算指令、二进制运算指令、增量/减量指令、逻辑运算指令、特殊运算指令等，这些指令多是类似汇编语言。另外PLC还提高了充足的计时器、计数器、内部继电器、寄存器及存贮区等内部资源，为编程带来极大方便。