COMMAND CODE - 98h or E5h

TYPE - Optional - Power Management Feature Set.

PROTOCOL - Non-data command.

INPUTS -

NORMAL OUTPUTS - The Sector Count register shall be set to written with a value of 0 (00h) if the device is in Standby mode. The Sector Count register may be set to written with a value of 128 (80h) if the device is in Idle Mode. The Sector Count register may be set to written with a value of 255 (FFh) if the device is in Active mode.

ERROR OUTPUTS - Aborted Command if the device does not support the Power Management feature set.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - If the device is in the Standby Mode the device shall set the BSY bit, set the Sector Count register to 0 (00h), clear the BSY bit, and assert INTRQ.

If the device is in the Idle Mode, the device shall set BSY, may set the Sector Count register to 128 (80h), clear BSY, and assert INTRQ.

If the device is in Active Mode, the device shall set the BSY bit, may set the Sector Count register to 255 (FFh), clear the BSY bit, and assert INTRQ.

COMMAND CODE - DEh

TYPE - Optional - Removable.

PROTOCOL - Non-data command.

INPUTS -

NORMAL OUTPUTS - None.

ERROR OUTPUTS - If the device is not ready or is not capable of locking the media, the ABRT bit in the Error register and the ERR bit in the Status register shall be returned set to one.

If the device is already locked and the media change request button is active, then a Media Change Requested status shall be returned by setting the MCR bit to one in the Error register and the ERR bit in the Status register to one.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - This command either locks the device or media, or provides the status of the media change request button.

If the device is not locked, the device shall be set to the locked state and good status returned no error set.

If the device is locked, the status returned shall indicate the state of the media change request button. Good status No error shall be returned set while the media change request button is not active, and the MCR bit in the Error register and the ERR bit in the Status register shall be returned set to one when the media change request button is active.

When a device is in a DOOR LOCKED state, the device shall not respond to the media change request button, except by setting the MCR status bit to one, until the DOOR LOCKED condition is cleared. A DOOR LOCK condition shall be cleared by a DOOR UNLOCK or MEDIA EJECT command, or by a hardware device reset. See 7.4.

Note 11 - Some caching controllers not reporting ATA-3 capability hang if issued this command.

COMMAND CODE - DFh

TYPE - Optional - Removable.

PROTOCOL - Non-data command.

INPUTS -

NORMAL OUTPUTS - None.

ERROR OUTPUTS - If the device does not support this command or is not ready, then the ABRT bit shall be returned set to one in the Error register and the ERR bit shall be returned set to one in the Status register.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - This command shall unlock the device, if it is locked, and shall allow the device to respond to the media change request button. See 7.4.

Note 12 - Some caching controllers not reporting ATA-3 capability hang if issued this command.

COMMAND CODE - 92h

TYPE - Optional.

PROTOCOL - PIO data out.

INPUTS - The head bits of the Device/Head register shall always be set to zero. The Cylinder High and Low registers shall be set to zero. The Sector Number and Sector Count registers are used together as a 16-bit sector count value. The Feature register specifies the subcommand code.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the device does not support this command or did not accept the microcode data. Aborted error if subcommand code not a supported value.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - This command enables the host to alter the device’s microcode. The data transferred using the DOWNLOAD MICROCODE command is vendor specific.

All transfers shall be an integer multiple of the sector size. The size of the data transfer is determined by the contents of the Sector Number Register and the Sector Count register. The Sector Number Register shall be used to extend the Sector Count register, to create a sixteen bit sector count value. The Sector Number Register shall be the most significant eight bits and the Sector Count register shall be the least significant eight bits. A value of zero in both the Sector Number Register and the Sector Count register shall indicate no data is to be transferred. This allows transfer sizes from 0 bytes to 33 553 920 bytes, in 512 byte increments.

The Features register shall be used to determine the effect of the DOWNLOAD MICROCODE command. The values for the Feature Register are:

01h - download is for immediate, temporary use

07h - save downloaded code for immediate and future use

Either or both values may be supported. All other values are reserved.

COMMAND CODE - 90h

TYPE - Mandatory.

PROTOCOL - Non-data.

INPUTS - None. The device selection bit in the Device/Head register is ignored.

NORMAL OUTPUTS - The diagnostic code written into the Error register is an 8-bit code as shown in Table 8, and not as defined in 6.2.9.

PREREQUISITES - None.

DESCRIPTION - This command shall perform the internal diagnostic tests implemented by the device. See also 6.2.9 and 6.2.13. The DEV bit in the Device/Head register is ignored. Both devices, if present, shall execute this command.

Device 0 performs the following operations for this command:

a)Device 0 sets the BSY bit within 400 ns after the EXECUTE DEVICE DIAGNOSTIC command is received;

b)Device 0 performs diagnostics;

c)Device 0 resets the Command Block registers to the following:

	Cylinder Low	=	00h		Cylinder High	=	00h
	Sector Count	=	01h		Device/Head	=	00h
	Sector Number	=	01h

d)Device 0 posts diagnostic results to bits 6-0 of the Error Register;

e)If Device 0 detected that Device 1 is present during the most recent power on or hardware reset sequence, then Device 0 waits up to 6 s from the time that the EXECUTE DEVICE DIAGNOSTIC command was received for Device 1 to assert PDIAG-. If PDIAG- is asserted within 6 s, Device 0 clears bit 7 to zero in the Error Register, else Device 0 sets bit 7 equal to 1 in the Error Register.

If device 1 was not detected during the most recent power up or hardware reset sequence, then Device 0 clears bit 7 to zero in the Error register;

f)Device 0 clears the BSY bit when ready to accept commands that do not require the DRDY bit to be equal to 1.Device 0 shall clear the BSY bit within 6 s from the time that the EXECUTE DEVICE DIAGNOSTIC command was received;

g)Device 0 sets the DRDY bit when ready to accept any command.

NOTE 13: Steps f) and g) may occur at the same time. While no maximum time is specified for the DRDY bit to be set to one to occur, a host is advised to allow at least 30 s for the DRDY bit to be set to one. See Figure 7.

Device 1 performs the following operations for this command:

a)Device 1 sets the BSY bit within 400 ns after the EXECUTE DEVICE DIAGNOSTIC command is received;

b)Device 1 negates PDIAG- within 1 ms after the command is received;

c)Device 1 performs diagnostics;

d)Device 1 resets the Command Block registers to the following:

	Cylinder Low	=	00h		Cylinder High	=	00h
	Sector Count	=	01h		Device/Head	=	00h
	Sector Number	=	01h

e)Device 1 clears bit 7 of the Error register to zero and posts its diagnostic results to bits 6 through 0 of Error register;

f)Device 1 clears the BSY bit when ready to accept commands that do not require the DRDY bit to be equal to one;

g)If Device 1 passed its diagnostics without error in step c), Device 1 asserts PDIAG-. If the diagnostics failed, Device 1 does not assert PDIAG- and continues to the next step;

NOTE 14: Device 1 shall clear the BSY bit and assert PDIAG- within 5 s of the time that the EXECUTE DEVICE DIAGNOSTIC command is received.

h)Device 1 sets the DRDY bit when ready to accept any command.

NOTE 15: Steps f), g) and h) may occur at the same time. While no maximum time is specified for the DRDY bit to set to one, a host is advised to allow at least 30 s for the DRDY bit to be equal to one. See Figure 7.

COMMAND CODE - 50h

TYPE - Vendor specific.

PROTOCOL - Vendor specific.

INPUTS -

NORMAL OUTPUTS - Vendor specific.

ERROR OUTPUTS - Aborted Command if the device does not support this command. All other errors are vendor specific.

PREREQUISITES - DRDY set to one. Other prerequisites are vendor specific.

DESCRIPTION - The implementation of the FORMAT TRACK command is vendor specific. It is recommended that system implementations not utilize this command.

COMMAND CODE - ECh

TYPE - Mandatory

PROTOCOL - PIO data in.

INPUTS -

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - None.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - The IDENTIFY DEVICE command enables the host to receive parameter information from the device.

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, prepares to transfer the 256 words of device identification data to the host, sets the DRQ bit, clears the BSY bit, and generates an interrupt. The host can then transfer the data by reading the Data register. The parameter words in the buffer have the arrangement and meanings defined in Table 9. All reserved bits or words shall be zero.

The F/V column indicates if the word or part of a word has fixed (F) contents that do not change, variable (V) contents that may change depending on the device state or the commands executed by the device, X for words with vendor specific data which may be fixed or variable, and R for reserved words which shall be zero. For removable media devices, the value of fields indicated as fixed (F) may change when media is removed or changed.

Some parameters are defined as a group of bits. A word which is defined as a set of bits is transmitted with indicated bits on the respective data bus bit (e.g., bit 15 appears on DD15).

Some parameters are defined as a sixteen bit value. A word which is defined as a sixteen bit value places the most significant bit of the value on bit DD15 and the least significant bit on bit DD0.

Some parameters are defined as 32 bit values (e.g., words 57 and 58). Such fields are transferred using two word transfers. The device shall first transfer the least significant bits, bits 15 through 0 of the value, on bits DD (15:0) respectively. After the least significant bits have been transferred, the most significant bits, bits 31 through 16 of the value, shall be transferred on DD (15:0) respectively.

Some parameters are defined as a string of ASCII characters. For the string "Copyright", the character ‘C’ is the first byte, ‘o’ is the 2nd byte, etc. When such fields are transferred, the order of transmission is:

the 1st character (‘C’) is on bits DD (15:8) of the first word

the 2nd character (‘o’) is on bits DD (7:0) of the first word

the 3rd character (‘p’) is on bits DD (15:8) of the second word

the 4th character (‘y’) is on bits DD (7:0) of the second word

etc.

COMMAND CODE - EEh

TYPE - Optional

PROTOCOL - DMA

INPUTS -

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - None.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - The IDENTIFY DEVICE DMA command enables the host to receive parameter information from the device in DMA mode. The command transfers the same 256 words of device identification data as transferred by the IDENTIFY DEVICE command.

COMMAND CODE - 97h or E3h

TYPE - Optional - Power Management Feature Set.

PROTOCOL - Non-data command.

INPUTS - The value in the Sector Count register when the IDLE command is issued shall determine the time period programmed into the Standby Timer. See Table 11.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - This command causes the device to set the BSY bit, enter the Idle Mode, clear the BSY bit, and assert INTRQ. INTRQ is asserted even though the device may not have fully transitioned to Idle Mode.

If the Sector Count register is non-zero then the Standby Timer shall be enabled. The value in the Sector Count register shall be used to determine the time programmed into the Standby Timer. See 7.3.

If the Sector Count register is zero then the Standby Timer is disabled.

COMMAND CODE - 95h or E1h

TYPE - Optional - Power Management Feature Set.

PROTOCOL - Non-data command.

INPUTS -

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command - The device does not support the Power Management feature set.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - This command causes the device to set the BSY bit, enter the Idle Mode, clear the BSY bit, and assert INTRQ. INTRQ is asserted even though the device may not have fully transitioned to Idle Mode. See 7.3.

COMMAND CODE - 91h

TYPE - Mandatory.

PROTOCOL - Non-data.

INPUTS - The Sector Count register specifies the number of logical sectors per logical track, and the Device/Head register which specifies the maximum head number.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the device does not support the requested CHS translation.

PREREQUISITES - None.

DESCRIPTION - This command enables the host to set the number of logical sectors per track and the number of logical heads minus 1, per logical cylinder for the current CHS translation mode.

Upon receipt of the command, the device sets the BSY bit, saves the parameters, clears the BSY bit, and generates an interrupt.

A device shall support the CHS translation described in words 1, 3 and 6 of the IDENTIFY DEVICE information. Support of other CHS translations is optional.

If the requested CHS translation is not supported, the device shall set the Error bit in the Status register and set the Aborted Command bit in the Error register before clearing the BSY bit in the Status register.

If the requested CHS translation is not supported, the device shall fail all media access commands with an ID Not Found error until a valid CHS translation is established.

COMMAND CODE - EDh

TYPE - Optional - Removable.

PROTOCOL - Non-data.

INPUTS -

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - If the device does not support this command, the device shall return a Command Abort error.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - This command completes any pending operations, spins down the device if needed, unlocks the door or media if locked, and initiates a media eject, if required.

COMMAND CODE - 00h

TYPE - Optional.

PROTOCOL - Non-data.

INPUTS -

NORMAL OUTPUTS - The Command Block registers, other than the Error and Status registers, are not changed by this command. This command always fails with an Aborted Command error.

ERROR OUTPUTS - None.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - This command enables a host, which can only perform 16-bit register accesses, to check device status. The device shall respond, as it does to an unrecognized command, by setting Aborted Command in the Error register, Error in the Status register, clearing Busy in the Status register, and asserting INTRQ.

COMMAND CODE - E4h

TYPE - Optional.

PROTOCOL - PIO data in.

INPUTS -

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported.

PREREQUISITES - DRDY set equal to one. A WRITE BUFFER command shall immediately proceed a READ BUFFER command.

DESCRIPTION - The READ BUFFER command enables the host to read the current contents of the device’s sector buffer. When this command is issued, the device sets the BSY bit, sets up the sector buffer for a read operation, sets the DRQ bit, clears the BSY bit, and generates an interrupt. The host then reads the data from the buffer.

The READ BUFFER and WRITE BUFFER commands shall be synchronized such that sequential WRITE BUFFER and READ BUFFER commands access the same 512 bytes within the buffer.

COMMAND CODE - 22h (with retries) or 23h (without retries)

TYPE - Optional.

PROTOCOL - PIO data in.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number specify the starting sector address to be read. The Sector Count register shall not specify a value other than one.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported. An unrecoverable error encountered during the execution of this command results in the termination of the command and the Command Block registers contain the sector address of the sector where the first unrecoverable error occurred. The amount of data transferred is indeterminant.

PREREQUISITES - DRDY set equal to one. The SET FEATURES subcommand to enable more than 4 vendor specific bytes shall be executed prior to the READ LONG command if other than 4 vendor specific bytes are to be transferred. The READ LONG command shall be immediately preceded by a Write LONG command.

DESCRIPTION - The READ LONG command performs similarly to the READ SECTOR(S) command except that it returns the data and a number of vendor specific bytes appended to the data field of the desired sector. During a READ LONG command, the device does not check to determine if there has been a data error. Only single sector READ LONG operations are supported.

The transfer of the vendor specific bytes shall be 16 bit transfers with the vendor specific byte in bits 7 through 0. Bits 15 through 8 shall be ignored by the host. BIOS and driver developersThe host shall use PIO mode 0 when using this command.

Error recovery performed by the device either with or without retries is vendor specific.

Note 21 - The committee is considering removing READ LONG and WRITE LONG commands in future versions of this a future ATA standard.

COMMAND CODE - C4h

TYPE - Mandatory

PROTOCOL - PIO data in.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number specify the starting sector address to be read. The Sector Count register specifies the number of sectors to be transferred.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - An unrecoverable error encountered during the execution of this command results in the termination of the command and the Command Block registers contain the sector address of the sector where the first unrecoverable error occurred. The amount of data transferred is indeterminant.

PREREQUISITES - DRDY set equal to one. If bit 8 of Word 59 of the IDENTIFY DEVICE response is cleared to zero, a successful SET MULTIPLE MODE command shall precede a READ MULTIPLE command.

DESCRIPTION - The READ MULTIPLE command performs similarly to the READ SECTOR(S) command. Interrupts are not generated on every sector, but on the transfer of a block which contains the number of sectors defined by a SET MULTIPLE MODE command or the default if no intervening SET MULTIPLE command has been issued. Command execution is identical to the READ SECTOR(S) operation except that the number of sectors defined by a SET MULTIPLE MODE command are transferred without intervening interrupts. The DRQ bit qualification of the transfer is required only at the start of the data block, not on each sector.

The block count of sectors to be transferred without intervening interrupts is programmed by the SET MULTIPLE MODE command, which shall be executed prior to the READ MULTIPLE command. When the READ MULTIPLE command is issued, the Sector Count register contains the number of sectors (not the number of blocks or the block count) requested.

If the number of requested sectors is not evenly divisible by the block count, as many full blocks as possible are transferred, followed by a final, partial block transfer. The partial block transfer shall be for n sectors, where n = remainder (sector count/ block count)

If the READ MULTIPLE command is attempted when READ MULTIPLE commands are disabled, the READ MULTIPLE operation shall be rejected with an Aborted Command error.

Device errors encountered during READ MULTIPLE commands are posted at the beginning of the block or partial block transfer, but the DRQ bit is still set and the data transfer shall take place as it normally would, including transfer of corrupted data, if any. The contents of the Command Block Registers following the transfer of a data block which had a sector in error are undefined. The host should retry the transfer as individual requests to obtain valid error information.

Subsequent blocks or partial blocks are transferred only if the error was a correctable data error. All other errors cause the command to stop after transfer of the block which contained the error. Interrupts are generated when the DRQ bit is set at the beginning of each block or partial block.

COMMAND CODE - 20h (with retries) or 21h (without retries)

TYPE - Mandatory.

PROTOCOL - PIO data in.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number specify the starting sector address to be read. The Sector Count register specifies the number of sectors to be transferred.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - An unrecoverable error encountered during the execution of this command results in the termination of the command and the Command Block registers contain the sector address of the sector where the first unrecoverable error occurred. The amount of data transferred is indeterminant.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - This command reads from 1 to 256 sectors as specified in the Sector Count register. A sector count of 0 requests 256 sectors. The transfer begins at the sector specified in the Sector Number register.

The DRQ bit is always set prior to data transfer regardless of the presence or absence of an error condition.

Error recovery performed by the device either with or without retries is vendor specific.

COMMAND CODE - 40h (with retries) or 41h (without retries)

TYPE - Mandatory.

PROTOCOL - Non-data.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number specify the starting sector address to be verified. The Sector Count register specifies the number of sectors to be verified.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - An unrecoverable error encountered during the execution of this command results in the termination of the command and the Command Block registers contain the sector address of the sector where the first unrecoverable error occurred.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - This command is identical to the READ SECTOR(S) command, except that the DRQ bit is never set, and no data is transferred to the host.

When the requested sectors have been verified, the device clears the BSY bit and generates an interrupt.

Error recovery performed by the device either with or without retries is vendor specific.

COMMAND CODE - 10h

TYPE - Optional.

PROTOCOL - Non-data.

INPUTS -

NORMAL OUTPUTS - If the command is executed in CHS addressing, Cylinder High, Cylinder Low and the head portion of Device/Head shall be zero. The Sector Number register shall be 1. If the command is executed in LBA addressing, the Cylinder High, Cylinder Low, the head portion of the Device/Head and the Sector Number register shall be zero.

ERROR OUTPUTS - If the device cannot reach cylinder 0, a Track 0 Not Found error is posted.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - The function performed by this command is vendor specific.

COMMAND CODE - BFh or F6h

TYPE - Optional - Security mode feature set.

PROTOCOL - PIO data out.

INPUTS -

NORMAL OUTPUTS - None.

ERROR OUTPUTS - Device returns Aborted command error if command is not supported, the device is in Locked mode, or the device is in Frozen mode.

PREREQUISITES - Device shall be in Unlocked mode.

DESCRIPTION - The SECURITY DISABLE PASSWORD command requests a transfer of a singlre sector of data from the host including the information specified in Table 12. Then the device checks the transferred password. If the User password or the Master password match, the device disables the lock function. This command does not change the Master password which may be reactivated later by setting a User password.

COMMAND CODE - BCh or F3h

TYPE - Optional - Security mode feature set.

PROTOCOL - Non-data.

INPUTS -

NORMAL OUTPUTS - None.

ERROR OUTPUTS - Device returns Aborted command error if command is not supported, the device is in Locked mode, or the device is in Frozen mode.

PREREQUISITES - None

DESCRIPTION - The SECURITY ERASE PREPARE command shall be issued immediately before the SECURITY ERASE UNIT command to enable device erasing and unlocking. This command is to prevent accidental erasure of the device.

COMMAND CODE - BDh or F4h

TYPE - Optional - Security mode feature set.

PROTOCOL - PIO data out.

INPUTS -

NORMAL OUTPUTS - None.

ERROR OUTPUTS - Device returns Aborted command error if command is not supported, the device is in Locked mode, or the device is in Frozen mode.

PREREQUISITES - This command must be immediately preceded by a SECURITY ERASE PREPARE command.

DESCRIPTION - This command requests to transfer a single sector of data from the host as decsribed in Table 12. If the password does not match then the device rejects the command with an Aborted error.

The SECURITY ERASE UNIT command erases all user data. The SECURITY ERASE PREPARE command shall be completed immediately prior to the SECURITY ERASE UNIT command. If the device receives a SECURITY ERASE UNIT command without an immediately prior SECURITY ERASE PREPARE command, the device aborts the SECURITY ERASE UNIT command

This command disables the device lock function, however, the master password is still stored internally within the device and may be reactivated later when a new user password is set.

COMMAND CODE - BAh or F1h

TYPE - Optional - Security mode feature set.

PROTOCOL - PIO data out.

INPUTS -

NORMAL OUTPUTS - None.

ERROR OUTPUTS - Device returns Aborted command error if command is not supported, the device is in Locked mode, or the device is in Frozen mode.

PREREQUISITES - None

DESCRIPTION - This command requests a transfer of a single sector of data from the host including the information specified in Table 13. The data transferred controls the function of this command.

COMMAND CODE - BBh or F2h

TYPE - Optional - Security mode feature set.

PROTOCOL - PIO data out.

INPUTS -

NORMAL OUTPUTS - None.

ERROR OUTPUTS - Device returns Aborted command error if command is not supported, or the device is in Frozen mode.

PREREQUISITES - None

DESCRIPTION - This command requests to transfer a single sector of data from the host as decsribed in Table 12

If the Identifier bit is set to master and the device is in high security level, then the password supplied shall be compared with the stored master password. If the device is in maximum security level then the unlock shall be rejected.

If the Identifier bit is set to user then the device compares the supplied password with the stored user password.

If the password compare fails then the device returns an abort error to the host and decrements the unlock counter. This counter is initially set to five and is decremented for each password mismatch, this includes password mismatches for all security commands when SECURITY UNLOCK is issued and the device is locked. When this counter reaches zero then all password protected SECURITY UNLOCK and SECURITY ERASE UNIT commands are rejected aborted until a power-on reset or a hard reset. SECURITY UNLOCK commands issued when the device is unlocked have no effect on the unlock counter.

COMMAND CODE - 70h

TYPE - Mandatory.

PROTOCOL - Non-data.

INPUTS - The Cylinder High, Cylinder Low, head portion of the Device/Head register and the Sector Number register contain the sector address to which the device may move the read/write heads.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Error reporting is vendor specific.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - The function performed by this command is vendor specific, and may or may not aeffect the position of the read/write heads.

COMMAND CODE - EFh

TYPE - The command is mandatory.Each subcommand is optional.

PROTOCOL - Non-data.

INPUTS - The Feature register contains a subcommand code as described in Table 15. Some subcommands use other registers, such as the Sector Count register to pass additional information to the device.

NORMAL OUTPUTS - See the subcommand descriptions.

ERROR OUTPUTS - If any subcommand input value is not supported or is invalid, the device posts an Aborted Command error.

PREREQUISITES - None.

DESCRIPTION - This command is used by the host to establish the following parameters which affect the execution of certain device features as shown in Table 15.

At power on, or after a hardware reset, the default setting of the functions specified by the subcommands are vendor specific.

Vendor specific subcommand code ABh allows the host to request the device to set the maximum prefetch to the value in sectors contained in the Sector Count register. Error recovery performed by the device with or without retries is vendor specific.

COMMAND CODE - C6h

TYPE - Mandatory

PROTOCOL - Non-data.

INPUTS - The Sector Count register contains number of sectors per block to use on all following READ/WRITE MULTIPLE commands. It is recommended that tThe host shall set Sector Count values equal to 2, 4, 8, 16, 32, 64, or 128.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - If a block count is not supported, a Aborted Command error is posted.

PREREQUISITES - DRDY set Equal to one.

DESCRIPTION - This command establishes the block count for READ MULTIPLE and WRITE MULTIPLE commands.

Devices shall support the block size specified in the IDENTIFY DRIVE parameter word 47, bits 7 through 0, and may also support smaller values.

Upon receipt of the command, the device sets the BSY bit equal to one and checks the Sector Count register. If the Sector Count register contains a valid value and the block count is supported, the value is used for all subsequent READ MULTIPLE and WRITE MULTIPLE commands and their execution is enabled.

COMMAND CODE - 99h or E6h

TYPE - Optional - Power Management Feature Set.

PROTOCOL - Non-data command.

INPUTS -

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command - The device does not support the Power Management feature set.

PREREQUISITES - DRDY set equal to one.

DESCRIPTION - This command is the only way to cause the device to enter Sleep Mode.

This command causes the device to set the BSY bit, prepare to enter Sleep mode, clear the BSY bit and assert INTRQ. The host shall read the Status register in order to clear the interrupt and allow the device to enter Sleep mode. In Sleep mode the interface becomes inactive without affecting the operation of the ATA interface. The host shall not attempt to access the Command Block registers while the device is in Sleep mode.

Because some host systems may not read the Status register and clear the interrupt, a device may automatically deassert INTRQ and enter Sleep mode after a vendor specific time period of not less than 2 s.

The only way to recover from Sleep Mode is with a software reset or a hardware reset.

A device shall not power on in Sleep Mode nor remain in Sleep Mode following a reset sequence.