1)系统程序存储器
PLC系统程序决定了PLC的基本功能，该部分程序由PLC制造厂家编写并固化在系统程序存储器中，主要有系统管理
程序、用户指令解释程序和功能程序与系统程序调用等部分。
系统管理程序主要控制PLC的运行，使PLC按正确的次序工作;户指令解释程序将PLC的用户指令转换为机器语言
指令，传输到CPU内执行;功能程序与系统程序调用则负责调用不同的功能子程序及其管理程序。
系统程序属于需长期保存的重要数据，所以其存储器采用ROM或EPROM。ROM是只读存储器，该存储器只能读出
内容，不能写入内容，ROM具有非易失性，即电源断开后仍能保存已存储的内容。
EPEROM为可电擦除只读存储器，须用紫外线照射芯片上的透镜窗口才能擦除写入内容，可电擦除可编程只读存储
器还有E2PROM、FLASH等。
Death 71 day white middle
The memory in PLC is mainly used to store system programs, user programs, data, etc.
1) System program memory
The PLC system program determines the basic functions of PLC. This part of the program is written by the PLC manufacturer and solidified in the system program memory, mainly including system management
Program, user instruction interpreter, function program and system program call.
The system management program mainly controls the operation of PLC to make PLC work in the correct order; The user instruction interpreter converts the user instructions of PLC into machine language
Instructions, transmitted to the CPU for execution; Function program and system program call are responsible for calling different function subroutines and their management programs.
The system program is an important data that needs to be stored for a long time, so its memory adopts ROM or EPROM. ROM is read-only memory, which can only be read out
The content cannot be written. The ROM is nonvolatile, that is, the stored content can still be saved after the power is disconnected.
Eperom is an electrically erasable read-only memory, and the written content can be erased only by irradiating the lens window on the chip with ultraviolet light. It is an electrically erasable programmable read-only memory
There are E2PROM, flash, etc.
客服1