external interrupt using by keypad encoder 74c922

[denesio]

here is a code:

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const char key_table[16] = "123A456B789C*0#D";
unsigned char key;
//unsigned char ex0_isr_counter = 0;

void ex0_isr (void) interrupt 0
{
//ex0_isr_counter++;   // Increment the count
unsigned char keypad_scan;
    key = ((keypad_scan=keypad_address)&keypad_mask);
  	key = key_table[key];
	goto_xy(0,0);
	putch_lcd(key); 
}
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   while(1)
    	{
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if (key == 4)
{
   goto_xy(2,0);
   putch_lcd(0xe4); 
   Puts("vse-vse");
   }
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}

why in first time the message is printed to lcd (interrupt isr),
and second time is not (if (key == 4)).......
"key" is global variable..........

 

[yogi]

which microcontroller are you using. See my code for AVR microcontroller
**broken link removed**

Bibin John
www.bibinjohn.tk

 

[denesio]

i am using 89c51rd2..
it is working properly now...

#define keypad_mask 0x0F 
#define keypad_address (*((unsigned char xdata*)0x8007)) 
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const char code key_table[16] = "123A456B789C*0#D"; 
unsigned char key; 
unsigned char key_lcd; 
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void ex0_isr (void) interrupt 0 
{ 
unsigned char keypad_scan; 
key = ((keypad_scan=keypad_address)&keypad_mask); 
key_lcd = key_table[key]; 
goto_xy(19,0); 
putch_lcd(key_lcd); 
} 
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switch (key) 
{ 
// goto_xy(1,1); 
case 0 : LCD_clear_row(1); goto_xy(0,1); Puts(buffer); goto_xy(17,0); putch_lcd('0'); break; 
case 1 : LCD_clear_row(1); goto_xy(0,1); rtc_time_to_lcd1(); goto_xy(17,0); putch_lcd('1'); break; 
case 2 : LCD_clear_row(1); goto_xy(17,0); putch_lcd('2'); break; 
case 3 : LCD_clear_row(1); goto_xy(17,0); putch_lcd('3'); break; 
case 4 : LCD_clear_row(1); goto_xy(17,0); rtc_read_reg(); rtc_reg_to_lcd(); goto_xy(17,0); putch_lcd('4'); break; 
case 5 : LCD_clear_row(1); goto_xy(0,1); rtc_reg_to_lcd1(); goto_xy(17,0); putch_lcd('5'); break; 
case 6 : LCD_clear_row(1); goto_xy(17,0); putch_lcd('6'); break; 
case 7 : LCD_clear_row(1); goto_xy(17,0); putch_lcd('7'); break; 
case 8 : LCD_clear_row(1); goto_xy(17,0); putch_lcd('8'); break; 
case 9 : LCD_clear_row(1); goto_xy(17,0); putch_lcd('9'); break; 
case 10 : LCD_clear_row(1); goto_xy(17,0); putch_lcd('A'); break; 
case 11 : LCD_clear_row(1); goto_xy(17,0); putch_lcd('B'); break; 
case 12 : LCD_clear_row(1); goto_xy(17,0); putch_lcd('C'); break; 
case 13 : LCD_clear_row(1); goto_xy(17,0); putch_lcd('D'); break; 
case 14 : LCD_clear_row(1); goto_xy(17,0); putch_lcd('E'); break; 
case 15 : LCD_clear_row(1); goto_xy(0,1); rtc_read_time(); rtc_time_to_lcd(); goto_xy(17,0); putch_lcd('F'); break; 
} 

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