T13/e05131r0
Proposal to Clarify the Meaning of IDENTIFY DEVICE
June 14, 2005
Technical Editor: Curtis E. Stevens Western Digital Technologies Inc. 20511 Lake Forest Dr. Lake Forest, Ca. 92630 E-Mail: Curtis.Stevens@wdc.com Phone: 949-672-7933
Proposal to Clarify the Meaning of IDENTIFY DEVICE
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T13/e05131r0
1 Introduction
The purpose of this proposal is to clarify the relationship of IDENTIFY DEVICE feature reporting to implementation of the feature. Currently there is no stated requirement in ATA/ATAPI-7 and below that a host check IDENTIFY DEVICE before using optional commands. As a result, it is possible that a device manufacturer could disable a feature and an ATA/ATAPI-7 compliant host could try to use the feature anyway. This could lead to indeterminate results when an unsupported command is executed.
2 IDENTIFY DEVICE Description
The IDENTIFY DEVICE command enables the host to receive parameter information from the device. See Table 15 for a description of the return data. Some devices may have to read the media in order to complete this command. When the command is issued, the device sets the BSY bit to one, prepares to transfer the 256 words of device identification data to the host, sets the DRQ bit to one, clears the BSY bit to zero, and asserts INTRQ if nIEN is cleared to zero. The host may then transfer the data by reading the Data register. Table 15 defines the arrangement and meaning of the parameter words in the buffer. All reserved bits or words shall be zero. [Editors Note: Need to rework this to stay away from BSY/DRQ] The parameter information contains data regarding optional feature or command support. The host shall not issue an optional command unless support is indicated in the parameter information. If the host issues a command that is indicated as not supported, the drive may produce indeterminate results. Some parameters are defined as a 16-bit value. A word that is defined as a 16-bit value places the most significant bit of the value on signal line DD15 and the least significant bit on signal line DD0 (See 3.2.6). For serial implementation see 3.2.7. Some parameters are defined as 32-bit values (e.g., words (61:60)). Such fields are transferred using two successive word transfers. The device shall first transfer the least significant bits, bits (15:0) of the value, on signal lines DD(15:0) respectively. After the least significant bits have been transferred, the most significant bits, bits (31:16) of the value, shall be transferred on DD(15:0) respectively (See 3.2.6). Some parameters are defined as a string of ACSII characters. Such fields are transferred as defined in 3.2.6
Proposal to Clarify the Meaning of IDENTIFY DEVICE
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