Questions regarding Mico + Watchdog + EEPROM + LCD

[John Doe]

Hey guys, great forum you’ve got here. Long time reader first time poster.

My Setup:
-AT89c51: Micro for the brain, which is driven by a quartz crystal 7.37~ MHz

-MAX1232CPA: The supervisor for power supply and hardware failures, plus performs reset on micro at boot.

-24LC64: The EEPROM which connects to Micro to get SDA and SCL.

-16×1 LCD: Displays what I programmed.. yada yada

 

Now I do have other elements of the circuit but in my eyes these are the only things that should effect the LCD other than the actual power source itself. Power source is simple 12v DC power brick. I have VCC at ~5v to drive most, and 12v for things that need more juice like the LCD.

Why I say the other elements have no bearing on the display is because a display should be able to run off just these components. I have a working board of the same style and I can pull all other chips and that display will continue to work just fine.

My Problem:

I’m getting power, and contast to the LCD because I can even adjust to get black squares. Yet I’m getting no text to scroll. The chip and LCD are fine because tested them both in another board and they’re working as expected. I’m reading a continous voltage of 5v going from MAX1232 RST into RST pin of 89c51. Replaced MAX1232 to make sure wasn’t faulty, but same issue. It keeps RST at 5v and therefore won’t allow the 89c51 to actually initialize properly. I assume this is because there is a detected hardware failure somewhere else in the circuit? 

I’m not asking for specific answers, just relative behavior of these components. For example, am I correct assuming the MAX1232 is preventing 89c51 from initializing? Is this hardware failure being sensed by the MAX1232? If so should I be looking at component failures or more source and ground failures?/

Thanks so much! Any clarification will be much appreciated!

[AJISH ALFRED]

Hi John,

Welcome to the forum. 

I guess you are mutiplexing the pin with LCD and EEPROM. That could cause problems sometimes. It dosen’t mean that you can’t do that in such a way, but when you do be careful that the components are not get affecting each other.

We can help you better if you post your circuit diagram here.

[Author]

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