IBM DTTA-351010 Hard Drive Specifications - Page 45

Addressing of HDD Registers, Cabling

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6.2.5 Addressing of HDD Registers The host addresses the drive through a set of registers called the Task File. These registers are mapped into the host's I/O space. Two chip select lines (-CS0 and -CS1) and three address lines (DA00-02) 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 DA02 DA01 DA00 DIOR = 0 (Read) DIOW = 0 (Write) Command Block Registers 0 1 0 0 0 Data Reg. Data Reg. 0 1 0 0 1 Error Reg. Features Reg. 0 1 0 1 0 Sector count Reg. Sector count Reg. 0 1 0 1 1 Sector number Reg. Sector number Reg 0 1 1 0 0 Cylinder low Reg. Cylinder low Reg. 0 1 1 0 1 Cylinder high Reg. Cylinder high Reg. 0 1 1 1 0 Drive/Head Reg. Drive/Head Reg. 0 1 1 1 1 Status Reg. Command Reg. Control Block Registers 1 0 1 1 0 Alt. Status Reg. Device control Reg 1 0 1 1 1 Drive address Reg. Figure 29. I/O address map 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 status register contents before interrupt (the value is invalid). 6.2.6 Cabling The maximum cable length from the host system to the HDD plus circuit pattern length in the host system shall not exceed 18 inches. For higher data transfer application(>8.3MB/sec), a consideration in system design is recommended to reduce cable noise and/or cross-talk, such as shorter cable, bus termination, shielded cable, etc. Specification 37

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6.2.5
Addressing of HDD Registers
The host addresses the drive through a set of registers called the Task File.
These registers are mapped into
the host's I/O space.
Two chip select lines (-CS0 and -CS1) and three address lines (DA00-02) 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
DA02 DA01 DA00
DIOR = 0 (Read)
DIOW = 0 (Write)
Command Block Registers
0
1
0
0
0
Data Reg.
Data Reg.
0
1
0
0
1
Error Reg.
Features Reg.
0
1
0
1
0
Sector count Reg.
Sector count Reg.
0
1
0
1
1
Sector number Reg.
Sector number Reg
0
1
1
0
0
Cylinder low Reg.
Cylinder low Reg.
0
1
1
0
1
Cylinder high Reg.
Cylinder high Reg.
0
1
1
1
0
Drive/Head Reg.
Drive/Head Reg.
0
1
1
1
1
Status Reg.
Command Reg.
Control Block Registers
1
0
1
1
0
Alt. Status Reg.
Device control Reg
1
0
1
1
1
Drive address Reg.
Figure 29. I/O address map
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 acces-
sible.
For example, the host is not supposed to read status register contents before interrupt (the value is invalid).
6.2.6
Cabling
The maximum cable length from the host system to the HDD plus circuit pattern length in the host system
shall not exceed 18 inches.
For higher data transfer application(>8.3MB/sec), a consideration in system design is recommended to
reduce cable noise and/or cross-talk, such as shorter cable, bus termination, shielded cable, etc.
Specification
37