9.1.8 Addressing of registers
The host addresses the drive through a set of registers called the Task File. These registers are mapped
into the I/O space. Two chip select lines (CS0- and CS1-) and three address lines (DA0-02) are used to
select one of these registers, while a DIOR- or DIOW- is provided at the specified time.
The CS0- is used to address Command Block registers while the CS1- is used to address the Control
Block registers. The following table shows the I/O address map.
Device control Reg.Alt. Status Reg.01101
Control Block Registers
Command Reg. Status Reg. 11110
Drive/Head Reg.Drive/Head Reg.01110
Cylinder high Reg.Cylinder high Reg.10110
Cylinder low Reg.Cylinder low Reg.00110
Sector number Reg.Sector number Reg.11010
Sector count Reg.Sector count Reg.01010
Features Reg.Error Reg.10010
Data Reg.Data Reg.00010
Command Block Registers
DIOW- = 0 (Write)DIOR- = 0 (Read)DA0DA1DA2CS1-CS0-
Note: "Addr." field is shown just as an example.
During DMA operation (from writing to the command register until an interrupt) all registers are not
accessible. For example, the host is not supposed to read the status register contents before interrupt
—the value is invalid.
Figure 35. I/O address map
9.1.9 Cabling
The maximum cable length from the host system to the drive plus circuit pattern length in the host system
must not exceed 18 inches.
For data transfers greater than 8.3 MB/s it is recommended that designs measures are used to reduce
cable noise and cross-talk. Examples of design modification include use of shorter cable, bus termination,
and the use of shielded cable.
The 80-conductor ATA cable assembly (P/N SFF-8049) must be used for systems operating at
Ultra DMA modes 3, 4 and 5.
Deskstar 60 GXP Hard disk drive specification
40
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