Although 8-bit operation is included in the IDE interface, most hard disk drives do not support this mode. If you nonetheless want to control such drives with an 8-bit microcontroller, you will find the interface circuit described here to be essential.Hard disk drives as mass storage devices are an indispensable part of modern computers. A few years ago, they were large and expensive devices, but presently (and up until the next generation) they are available with enormous capacities and small physical dimensions at quite reasonable prices. Most contemporary computers use hard disk drives with IDE interfaces. Since this interface (which is also referred to as ATA) comes from the PC world and thus works with a 16-bit operating system, it is possible to use it directly with 8-bit controllers, albeit with some problems. Although the interface can be switched to the 8-bit operating mode, this does not always work in practice, since many hard disk drives do not support this option.