What is Parallel ATA (PATA)?
Parallel ATA (PATA) is based on the original IBM PC ISA bus. Basic PATA uses 5 address signals, two read/write signals, a 16-bit bidirectional data bus and an interrupt signal. These signals are used to access two blocks of 8-bit registers and one 16-bit register in the ATA or ATAPI device. These registers are used to send commands to a device, to receive status from the device and to transfer data in what is called PIO mode. Most PATA implementations also support a data transfer mode called DMA. DMA requires two additional signals. There are two DMA protocols: the old ISA MultiWord (MW) DMA and the newer UltraDMA. Many years ago there was also a very slow Single Word DMA protocol. There are some additional PATA signals that we can avoid talking about for now. Normally the PATA signals are used across a 40-wire or 80-wire PATA cable. But PCMCIA PC Card ATA or Compact Flash is another popular interface used by ATA devices. The rules for accessing the registers in an ATA or ATAPI devices
