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LCD 4-bit mode Data and Control on Same Port

I have a Keil C code for using 16x2 LCD in 4-bit mode. the code is working fine.........

Problem: If "RS", "E" control pins (on LCD) are on a different port than the Data port, the code works fine.......
But if the Data and Control Pins are on the Same Port, there's nothing appearing on the LCD.

please suggest any reason (and remedy if possible) for this.........

Controller: P89V51RD2 80c51 core 8-bit CPU with 64KB Flash, 1Kb RAM from NXP(Philips).
LCD Module: Hitachi HD44780 controller based 16x2 Alphanumeric Green Backlit LCD.

Parents

0 Neil Kurzman over 14 years ago in reply to Amit Das

Since you did not give use the pinout lets look at 1 function WITH the pre and \pre tags

void lcd_data (unsigned char dat)
{
   lcd_port = (((dat >> 4) & 0x0F)|LCD_EN|LCD_RS); // Write High Nibble
   lcd_port = (((dat >> 4) & 0x0F)|LCD_RS);

   lcd_port = ((dat & 0x0F)|LCD_EN|LCD_RS);       // Write Low Nibble
   lcd_port = ((dat & 0x0F)|LCD_RS);

   delayus(200);                                  // wait 400 uSec
   delayus(200);
}

 I ASSUME  the data is the lower nibble

Reply

0 Neil Kurzman over 14 years ago in reply to Amit Das

Since you did not give use the pinout lets look at 1 function WITH the pre and \pre tags

void lcd_data (unsigned char dat)
{
   lcd_port = (((dat >> 4) & 0x0F)|LCD_EN|LCD_RS); // Write High Nibble
   lcd_port = (((dat >> 4) & 0x0F)|LCD_RS);

   lcd_port = ((dat & 0x0F)|LCD_EN|LCD_RS);       // Write Low Nibble
   lcd_port = ((dat & 0x0F)|LCD_RS);

   delayus(200);                                  // wait 400 uSec
   delayus(200);
}

 I ASSUME  the data is the lower nibble

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