June 23, 2010 |
6.3 Removable Media
The distinction between "removable" disks numbered 00h through 7Fh and "fixed" disks numbered 80h through FFh differs from conventional INT 13h functions. Devices numbered 0 through 7Fh are not changed. They follow conventional INT 13h standards for floppy disk operation. Devices numbered 80h through FFh include traditional fixed disks, and now also include removable media devices that support media change notification as well as software locking and unlocking capabilities. Functions in this standard support these devices. The values returned in the AL register upon completion of an INT 13h Function are vendor specific. Table 10 describes the return codes that are supported for removable media devices.
Table 10 — Removable Media Return Codes
| Return Code | Description |
| B0h | Media Not Locked In Device |
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| B1h | Media Locked In Device |
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| B2h | Media Not Removable |
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| B3h | Media In Use |
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| B4h | Lock Count Exceeded |
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| B5h | Valid Eject Request Failed |
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| B6h | Media Present but Read Protected |
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6.4 INT 13h Interface Subsets |
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6.4.1 Overview |
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It is permissible for BIOS to support only certain subsets of the INT 13h extensions. These subsets are defined in this standard. If a subset is supported then all functions within that subset shall be supported. The supported subsets shall be determined via the Check Extensions Present function. If a function is not supported and that function is subsequently invoked; then the function rejects the request with CF = 1b and AH = 01h. There are three subsets defined. At least one of these shall be supported.
NOTE 1 — Conventional INT 13h may be used for media accessing if the Fixed Disk Access Subset is not present.
6.4.2 Fixed Disk Access Subset
These functions support basic access to devices using the device address packet structure (see table 11).
Table 11 — Fixed Disk Access
Function | Code |
Check Extensions Present (see 8.14) | 41h |
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Extended Read (see 8.15) | 42h |
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Extended Write (see 8.16) | 43h |
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Verify Sectors (see 8.17) | 44h |
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Obsolete | 47h |
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Get Device Parameters (see 8.20) | 48h |
Working Draft Enhanced Disk Drive - 4 | 17 |
