Logic Boards
Just a little writeup on logic boards.
First of all, there are two main components on a logic board. The display controller (the big chip) and the EEPROM or Flash memory. Then there may be some voltage regulators, but on some models they're built into the display controller.
The display controller is what drives the whole thing actually. It is a custom microprocessor that takes the analog or digital input and turns it into a format suitable for the row/column drivers of the LCD screen, taking care of scaling where needed. It also controls the inverter, reports the model number and capabilities to the computer, and displays the OSD. It also has a built-in service pattern generator - hence why the monitors with corrupted EEPROM go into an endless cycling of service patterns.
The EEPROM is what tells the controller what is what. Most display controllers are programmable, output pin functions can be swapped. This enables many different types of screens to be driven with exactly the same logic board. This is done in the firmware stored on the EEPROM. Communication between the display controller and the outside world (screen and inverter) is unidirectional - the controller doesn't give a rat's ass what it's driving, it just sends the signals. What is reported to the computer has been previously stored in the EEPROM, it is not read from the screen itself. A particular logic board can drive ANY screen which has the same pinout it was programmed for. And, at least in theory, a logic board can be programmed to drive ANY screen regardless of pin configuration, if it uses the same number of pins. You could probably also program a Pong game into it instead of the "check signal cable" message, or something like that.
Unfortunately the available info is scarce and manufacturers do their best to keep it secret. Once i get my hands on an EEPROM programmer i'll mess around with a logic board firmware and see what happens. At least for now, if you have a defective monitor with good logic board, KEEP IT. You never know what use you can find for it.
First of all, there are two main components on a logic board. The display controller (the big chip) and the EEPROM or Flash memory. Then there may be some voltage regulators, but on some models they're built into the display controller.
The display controller is what drives the whole thing actually. It is a custom microprocessor that takes the analog or digital input and turns it into a format suitable for the row/column drivers of the LCD screen, taking care of scaling where needed. It also controls the inverter, reports the model number and capabilities to the computer, and displays the OSD. It also has a built-in service pattern generator - hence why the monitors with corrupted EEPROM go into an endless cycling of service patterns.
The EEPROM is what tells the controller what is what. Most display controllers are programmable, output pin functions can be swapped. This enables many different types of screens to be driven with exactly the same logic board. This is done in the firmware stored on the EEPROM. Communication between the display controller and the outside world (screen and inverter) is unidirectional - the controller doesn't give a rat's ass what it's driving, it just sends the signals. What is reported to the computer has been previously stored in the EEPROM, it is not read from the screen itself. A particular logic board can drive ANY screen which has the same pinout it was programmed for. And, at least in theory, a logic board can be programmed to drive ANY screen regardless of pin configuration, if it uses the same number of pins. You could probably also program a Pong game into it instead of the "check signal cable" message, or something like that.
Unfortunately the available info is scarce and manufacturers do their best to keep it secret. Once i get my hands on an EEPROM programmer i'll mess around with a logic board firmware and see what happens. At least for now, if you have a defective monitor with good logic board, KEEP IT. You never know what use you can find for it.