1602 LCD related c51 programming

1. Writing data and instructions needs to be done on the rising edge of LCDEN level. To achieve this, you should: ensure that LCDEN=0 when the program executes other instructions;
LCDEN level must be pulled low immediately after completing the execution of read and write data and instructions;
Ensure that LCDEN=0 before executing the write data instruction sub-function. For example:

…
 LCDEN=0;
…
void write_dat(char a)
{
 char e=1;
 while(e)e=read();
 RS=1;
 RW=0;
 P0=a;
 LCDEN=1;
 for(e=127;e>0;e--);
 LCDEN=0;
}

It is not possible to only pull the LCDEN level down before pulling the LCDEN level up in the write data instruction sub-function without delay.

For example this is wrong:

void write_cmd(char a)
{
 char e=1;
 while(e)e=read();
 LCDEN=0;
 RS=0;
 RW=0;
 P0=a;
 LCDEN=1;
 for(e=127;e>0;e--);
}

2. If the screen scrolling mode is used, the video memory address set before writing data is the position where the cursor stops. For example

Enter "QQ 814921012"

Address setting: write_cmd(0x82);

The screen will finally display: 12_

 
3. When the program starts to initialize the screen, the clear screen command should be executed. The clear screen command should also be added in due course during the program.

4. The scrolling is to connect the first and last addresses to form a ring. After executing the scrolling command, the screen will scroll immediately, and it will scroll once each time it is executed.
 The two lines scroll together and cannot be separated.