The following content is a description of the errors that I personally encountered during my tenure as a BIOS engineer, as well as the reasons and solutions.
1.
Source of error: When adjusting LED lights, in addition to the necessary unlock and lock operations, some IO Reg must be read and written. In the F7 register of LDN B of DataSheet 6793, the function of this register is to adjust the LED on, off and blinking. Among them, bit5 can flip the low and high of the led. If there is no other place to read or write to the register, or erase bit5, the on and off functions will be reversed when the LED is controlled under bios. That is to say, the original function is on, but now it is off.
Cause of error: Bit5 was written by mistake, and the position was set to 1, which resulted in an error.
Error modification: F7 register again, no operation on bit5. Keep the default value.
Personal experience: Read the Spec carefully and carefully check the code written. Attached.
