IBM DTCA-24090 Hard Drive Specifications - Page 61

Addressing of drive Registers

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6.7 Addressing of drive Registers The host addresses the drive through a set of registers called a Task File. These registers are mapped into the host's I/O space. Two chip select lines (-HCS0 and -HCS1) and three address lines (HA00-02) are used to select one of these registers, while a -HIOR or -HIOW is provided at the specified time. The -HCS0 is used to address Command Block registers. while the -HCS1 is used to address Control Block registers. The following table shows the standard I/O address range for IBM PC-AT machines. Addr. CS0 CS1 HA2 HA1 HA0 HIOR = 0 (Read) HIOW = 0 (Write) Command Block Registers 1F0 0 1 0 0 0 Data Reg. Data Reg. 1F1 0 1 0 0 1 Error Reg. Features Reg. 1F2 0 1 0 1 0 Sector count Reg. Sector count Reg. 1F3 0 1 0 1 1 Sector number Reg. Sector number Reg. 1F4 0 1 1 0 0 Cylinder low Reg. Cylinder low Reg. 1F5 0 1 1 0 1 Cylinder high Reg. Cylinder high Reg. 1F6 0 1 1 1 0 Drive/Head Reg. Drive/Head Reg. 1F7 0 1 1 1 1 Status Reg. Command Reg. Control Block Registers 3F6 1 0 1 1 0 Alt. Status Reg. Device control Reg 3F7 1 0 1 1 1 Drive address Reg. Figure 36. Register Address Note: "Addr." field is shown just as an example. Electrical Interface Specifications 53

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6.7
Addressing of drive Registers
The host addresses the drive through a set of registers called a Task File.
These registers are mapped into
the host's I/O space.
Two chip select lines (-HCS0 and -HCS1) and three address lines (HA00-02) are used
to select one of these registers, while a -HIOR or -HIOW is provided at the specified time.
The -HCS0 is used to address Command Block registers.
while the -HCS1 is used to address Control Block
registers.
The following table shows the standard I/O address range for IBM PC-AT machines.
Addr.
CS0
CS1 HA2 HA1 HA0
HIOR = 0 (Read)
HIOW = 0 (Write)
Command Block Registers
1F0
0
1
0
0
0
Data Reg.
Data Reg.
1F1
0
1
0
0
1
Error Reg.
Features Reg.
1F2
0
1
0
1
0
Sector count Reg.
Sector count Reg.
1F3
0
1
0
1
1
Sector number Reg.
Sector number Reg.
1F4
0
1
1
0
0
Cylinder low Reg.
Cylinder low Reg.
1F5
0
1
1
0
1
Cylinder high Reg.
Cylinder high Reg.
1F6
0
1
1
1
0
Drive/Head Reg.
Drive/Head Reg.
1F7
0
1
1
1
1
Status Reg.
Command Reg.
Control Block Registers
3F6
1
0
1
1
0
Alt. Status Reg.
Device control Reg
3F7
1
0
1
1
1
Drive address Reg.
Figure 36. Register Address
Note:
"Addr." field is shown just as an example.
Electrical Interface Specifications
53