5.2 Logical Interface

5.2.2 Outline of the Shadow Block Register

Each transport layer in the host system and device has a block register, which is called a Shadow Block Register in the host system, and a Block Register in the device.

These registers are used when the host system issues a command to the device.

Table 5.3 Shadow Block Register

Command Block registers

Read

 

Write

 

 

 

 

 

 

 

 

 

Data Port

 

 

 

 

 

 

 

Error

 

Features

 

 

 

 

 

 

 

Sector Count (exp)

 

Sector Count

Sector Count (exp)

 

Sector Count

 

 

 

 

 

 

Sector Number (exp)

 

Sector Number

Sector Number (exp)

 

Sector Number

 

 

 

 

 

 

Cylinder Low (exp)

 

Cylinder Low

Cylinder Low (exp)

 

Cylinder Low

 

 

 

 

 

 

Cylinder High (exp)

 

Cylinder High

Cylinder High (exp)

 

Cylinder High

 

 

 

 

 

 

 

 

Device / Head

 

 

 

 

Status

 

Command

 

 

 

 

 

 

 

Control Block registers

 

 

 

Alternate Status

Device Control

 

 

 

 

 

 

Note: Each of the Sector Count, Sector Number, Cylinder Low, and Cylinder High fields has a higher-order field used for issuing the Ext command. The fields are called Sector Count exp, Sector Number exp, Cylinder Low exp, and Cylinder High exp, respectively. For information on writing data to these fields, see "Device Control Field."

C141-E280

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