Addressing Of Registers; Cabling; Figure 35. I/O Address Map - IBM IC35L020 - Deskstar 20 GB Hard Drive Specifications

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.
CS0- CS1- DA2
0 1 0
0 1 0
0 1 0
0 1 0
0 1 1
0 1 1
0 1 1
0 1 1
1 0 1
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.
DA1 DA0 DIOR- = 0 (Read)
0 0 Data Reg.
0 1 Error Reg.
1 0 Sector count Reg.
1 1 Sector number Reg.
0 0 Cylinder low Reg.
0 1 Cylinder high Reg.
1 0 Drive/Head Reg.
1 1 Status Reg.
1 0 Alt. Status Reg.
Deskstar 60 GXP Hard disk drive specification
DIOW- = 0 (Write)
Command Block Registers
Data Reg.
Features Reg.
Sector count Reg.
Sector number Reg.
Cylinder low Reg.
Cylinder high Reg.
Drive/Head Reg.
Command Reg.
Control Block Registers
Device control Reg.
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