The LCD controller status register (LCSR) contains bits that signal over- and under-run errors for both the input and output FIFOs, as well as the AC-bias pin transition count/LCD disabled/DMA base update ready/and DMA transfer bus error conditions. Each of these hardware-detected events signals an interrupt request to the interrupt controller.
Each of the LCD’s status bits signals an interrupt request as long as the bit is set. Once the bit is cleared, the interrupt is cleared. Read/write bits are called status bits; read-only bits are called flags. Status bits are referred to as “sticky” (that is, once set by hardware, must be cleared by software). Writing 1 to a sticky status bit clears it; writing zero has no effect. Read-only flags are set and cleared by hardware; writes have no effect.