Addressing Of Registers; Cabling; Figure 42. I/O Address Map - IBM DTLA-305040 - Deskstar 41.1 GB Hard Drive Specifications

7.2.5 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 of the host. 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 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
1 0 1

Figure 42. I/O address map

During DMA operation (from writing to the command register until an interrupt) all registers are not acces-
sible.
For example, the host is not supposed to read status register contents before interrupt (the value is in-
valid).

7.2.6 Cabling

The maximum cable length from the host system to the drive plus circuit pattern length in the host system
shall not exceed 18 inches.
For higher data transfer application (>8.3MB/sec) a modification in the system design is recommended to
reduce cable noise and/or cross-talk, such as a shorter cable, bus termination, or a shielded cable.
For systems operating with Ultra DMA mode 3 or 4, 80-conductor ATA cable assembly (SFF-8049) shall
be used.
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.
1 1 Drive address Reg.
Deskstar 40GV & 75GXP hard disk drive specifications
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.
40
–