由于PLC和计算机属于两类产品，经过几十年的发展都形成了自身的装置特点和软件工具。实际上的区别继续存在。
PLC用编程器或计算机编程，编程语言是梯形图、功能块图、顺序功能表图和指令表等。集散系统自身或用计算机结构形成组态构成开发系统环境。
特别提出的是与STD总线工控机的区别，无论从维修、安装和模件功能都很相似。PLC更适用于黑模式下运行，但在线运行时若要进行较大的程序修改，其能力略逊于STD工控机，但是从开关量控制而言，PLC的性能优于STD工控机。
总的来说，在选择控制器时，首先要从工程要求、现场环境和经济性等方面考虑。没有什么控制器绝对完善，也没有哪种产品绝对差，只能说选择更适用的产品。
PLC的综合经济分析
tested function blocks from actual engineering applications have been expanded. any complex control
The scheme can be realized by the combination of these function blocks.
The function blocks provided by the system mainly include the following categories:
o
Analog processing
o
digital processing
loop regulation
Logical sequence control
c
logic operation
Monitoring function
Collection function.
c
arithmetic operations
c
TCP/IP protocol communication interface
Modbus protocol communication interface
1EC870-5 protocol communication interface (Telecontrol)
4.2 Field Controller PS
Industrial” field controller PS is a special process control station, which is embedded with field bus communication interface for users to use
Fieldbus technology offers very flexible options. Each PS allows to insert 4 fieldbus interface cards (the card type can be different),
Each card is connected to 1 field bus to collect process data and diagnostic information from the bus, the interface card is easy to replace and plug and play
(Plug & Play), and can be plugged and unplugged.
The field controller PS has
