The 4-bit AC Bias line transitions-per-interrupt (ACBI) field is used to specify the number of LcdAC line transitions to count before setting the AC bias count status (ABC) bit in the LCD controller status register, which signals an interrupt request. After the LCD controller is enabled, the value in ACBI is loaded to a 4-bit down counter, and the counter decrements each time the AC bias line state is inverted. When the counter reaches zero it stops, and the AC bias count (ABC) bit is set in the status register. Once ABC is set, the 4-bit down counter is reloaded with the value in ACBI and is disabled until ABC is cleared. Once ABC is cleared by the CPU, the down counter is enabled, and again decrements each time the AC bias line is flipped. The number of AC bias line transitions between each interrupt request ranges from 0–15. Note that programming ACBI = 0h0000 disables the AC bias line transitions-per-interrupt function.