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[PIC] PIC18F2520 interface 16x2 LCD

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nis2311

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LCD Display is Working Well . When I POWER OFF the microcontroller and LCD DISPLAY also OFF , When I tried to power ON AFTER 3 Seconds means MICROCONTROLLER AND LCD WORKING WELL,
but when I POWER ON THE DEVICE suddenly after 1 seconds or below or repeatedly , the LCD DISPLAY SCRAMBLES. afterwards I will POWER OFF the device and I Tried to ON after 3 Seconds LCD DISPLAY Works well.


My project is working in POWER INTERRUPTION AREA , So I want to solve the bug
Give me an idea to solve this....................

I attached the SCRAMBLED DISPLAY ALSO
 

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Give me an idea to solve this
Click to expand...
I am really puzzled trying to understand how someone expect to have some help without posting any code nor schematic diagram.
 

Reconsider the PIC reset (MCLR) circuit.
 

I agree with Zuisti the problem is probably with the MCLR reset circuit, maybe the capacitor on the MLCR line does not have a discharge diode Show circuit.
 

I connected 5 Volt supply through 10 K resistor to the MCLR PIN of the MICROCONTROLLER.
Any components have to add ..........Help Me
 

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More likely, it's a problem of missing or incomplete LCD display initialization. The software relies on power-on-reset state of the LCD controller but fails if the controller isn't fully reset.

Implement LCD software reset according to datasheet. PIC brownout reset should be configured as well, worst case a power supply supervisory and hardware watchdog IC might be helpful.
 

Add a 200 ms delay as the first line in LCD Initialization routine. LCD needs some time to react.
 

The standard microcontroller's active low reset circuitry comprises not only a pull-up resistor, but also a capacitor and a diode which respectively provide the ability to filter possible glitches on the power bus (such as due to hot plugging the board to the power connector), but also allow the fast reset to avoid unespected behavior of the program during the voltage supply fall down, although not strictly necessary for this core which can detect it by proper flags.
 

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