Micro controller and EEPROM,,theory of operation.

[ramondo]

Sirs;
I am looking for guidance on the startup interaction of a basic TV micro, its ROM and EEPROM. My understanding(may be erroneous) is the TV firmware is on a ROM chip and given to Micro at powerup,Micro then looks to EEprom for currant settings and if received ok it continues with startup. If EEprom data is corrupt then Micro shuts down. I have been told that if the EEprom is erased (in circuit or out) and then the TV is powered again, the micro will load default values from firmware into the EEprom.
I have NOT been able to get confirmation of this. Any help or Aim me in the right direction would be GREATLY appreciated.

 

[ronsimpson]

Your question(s) do not have a simple answer. It depends on many things.
The ROM likely is programmed at the factory and can not be changed. But in some micros it can be erased and reprogrammed. (depends on computer)
The EEPROM likely is programmed with defaults at the time when the ROM is programmed. When the TV is first powered up it looks bad, and every one looks different. In the factory there is a process of calibrating or aligning the TV. Here the size and shape and colors are set to look right. Then these new values are stored in EEPROM. Later at your house if you want the picture to look bigger/smaller/brighter/...…. then new values are added.

If EEprom data is corrupt

There are many different answers, again.
Some TVs do not have a way of knowing if the data is corrupted. They would just use the bad data and the picture looks bad. Simple!
Some TVs do know if the data is corrupted. They would just not turn on.
Some TVs will load the default data. Like you said.

Some of the TVs I designed, we loaded into EEPROM the average of the last 1000 TVs. What values that made the last TVs work are averaged and used on the next TV. Some factories did not do this step.
Then we aligned the TV and stored the values for this TV.
Next the used can change some of the values.
If the EEPROM gets corrupted we can back up to the values as the set left the factory.

In some TVs we stored the "default" values in ROM so they could not get corrupted. At power up the computer tests to see if the EEPROM is blank or corrupted and if so copies ROM values to EEPROM. (these values are not good but better than nothing)

Hope this helps. Ron,

 

[Nigel Goodwin]

As suggested, 'some' TV's will (or would, we're talking old CRT models) upload factory defaults if the EEPROM is blank, so with EEPROM problems you can simply replace the old one with a new blank one and it will initialise on power up.

Most sets though require you to buy a ready programmed EEPROM and fit that - many years back in the old CRT days I used to keep a database of downloaded EEPROM files, so I could program my own.

Blanking a corrupt EEPROM, and letting it be reloaded (for the few sets that did), rarely gave a reliable and lasting repair.

 

[be80be]

Waste of time the chip more then likely had one too many writes.

 

[ronsimpson]

had one too many writes.

Or the power went off while wrighting.

 

[ramondo]

Thanks to all!!! (fastest reply's I've ever had) My main concern with this is to determine if a corrupt eeprom is causing a dead set (I have confirmed all power rails are ok-just no turn on). I would install a blank eeprom and power on set, that should rewrite eeprom and set should powerup. If that does not work then I would consider Micro at fault. I have programmer and installed new eeproms (mostly VIZIO- but cannot find data for Samsung UN22f5000AFXZA.
ADDITIONAL question. Does a firmware upgrade (via USB or Internet) contain the default eeprom data.

 

[Nigel Goodwin]

Thanks to all!!! (fastest reply's I've ever had) My main concern with this is to determine if a corrupt eeprom is causing a dead set (I have confirmed all power rails are ok-just no turn on). I would install a blank eeprom and power on set, that should rewrite eeprom and set should powerup. If that does not work then I would consider Micro at fault. I have programmer and installed new eeproms (mostly VIZIO- but cannot find data for Samsung UN22f5000AFXZA.
ADDITIONAL question. Does a firmware upgrade (via USB or Internet) contain the default eeprom data.

I wouldn't have thought so - however, now you've mentioned Samsung, they were one of the manufacturers that DID write default data to the EEPROM if you replace it with a blank one.

This was a good thing - because for years Samsung knowingly fitted sub-standard electrolytics in the power supplies, and these regularly failed (many even while under warranty) and trashed the EEPROM's. So a common repair was to fit decent caps in the PSU, and fit a new blank EEPROM.

 

[crutschow]

The ROM likely is programmed at the factory and can not be changed. But in some micros it can be erased and reprogrammed. (depends on computer)

Doesn't that make it an EEPROM also?

 

[be80be]

Samsung are as said bad caps but the rom gets wrote new settings and has some saved from the start. I fixed one that set rom using remote you. So i guess the needed code is in frimware. It was little 28 inch samsung. I fixed 2 of them for friends.
I fixed some 54 inch ones the rom went bad with the supply caps.
Some of the rest i messed with the rom would get wrote at power up.

But im not a tv repairman but ive played with a. Bunch of rom chips out of tv and crt.

 

[Nigel Goodwin]

Doesn't that make it an EEPROM also?

Or FLASH - or as was common, EEPROM renamed as FLASH by the marketing department.