Technical information

CHAPTER 3
Devices and Ports
38 Hard Disk Drive
ATA Signal Descriptions 3
Table 3-4 describes the signals on the ATA hard disk connector.
Table 3-4 Signals on the ATA hard disk connector
Signal
name Signal description
DA(0–2) Device address; used by the computer to select one of the
registers in the ATA drive. For more information, see the
descriptions of the CS0 and CS1 signals.
DD(0–15) Data bus; buffered from IOD(16–31) of the computer’s I/O
bus. DD(0–15) are used to transfer 16-bit data to and from the
drive buffer. DD(8–15) are used to transfer data to and from
the internal registers of the drive, with DD(0–7) driven high
when writing.
/CS0 Register select signal. It is asserted low to select the main task
file registers. The task file registers indicate the command, the
sector address, and the sector count.
/CS1 Register select signal. It is asserted low to select the additional
control and status registers on the ATA drive.
CSEL Cable select; not available on this computer (n.c.).
/DASP Device active or slave present; not available on this computer
(n.c.).
IORDY I/O ready; when driven low by the drive, signals the CPU to
insert wait states into the I/O read or write cycles.
/IOCS16 I/O channel select; not used on this computer (pulled low by
1 kΩ).
/DIOR I/O data read strobe.
/DIOW I/O data write strobe.
/DMACK Used by the host to initiate a DMA transfer in response to
DMARQ.
DMARQ Asserted by the device when it is ready to transfer data to or
from the host.