Seagate ST760211DE Set Features command, Features register values, Transfer mode, Read look-ahead

4.2.2Set Features command

This command is used by the host to establish parameters that affect the execution of certain drive features. The supported features determined by the value in the Features register are as shown in Table 10. Read look- ahead and write cache are enabled by default upon power on.

Table 10:		Features register values
	Feature	Description
	02h	Enable Write Cache
	03h	Set DMA and PIO transfer modes based on the value in the Sector Count register.
		Sector Count register values
		08h: Set PIO Transfer Mode 0
		09h: Set PIO Transfer Mode 1
		0Ah: Set PIO Transfer Mode 2
		0Bh: Set PIO Transfer Mode 3
		0Ch: Set PIO Transfer Mode 4
		20h: Set Multiword Transfer Mode 0.
		21h: Set Multiword Transfer Mode 1.
		22h: Set Multiword Transfer Mode 2.
		40h: Set Ultra DMA mode 0.
		41h: Set Ultra DMA mode 1.
		42h: Set Ultra DMA mode 2.
		44h: Set Ultra DMA mode 4.
	05h	Enable Advanced Power Management (APM) with APM level as in the Sector Count register .
		Sector Count register values
		0h : Reserved
		1h – 7Fh : Allow Spin-Down (Standby Mode)
		80h – FEh : Disallow Spin-Down (Low Power Idle Mode)
		FFh : Reserved
	55h	Disable Read Look-Ahead.
	82h	Disable Write Cache.
	85h	Disable Advanced Power Management (APM)
	AAh	Enable Read Look-Ahead .

The following drive features are set after a Power On Reset, Hardware Reset or Software Reset.

Transfer mode :

Power On Reset	PIO 4, MDMA 2
Hardware Reset	PIO 4, MDMA 2
Software Reset	Current setting
Read look-ahead :
Power On Reset	Enabled
Hardware Reset	Enabled
Software Reset	Current setting

Write Cache :

Power On Reset	Enabled
Hardware Reset	Enabled
Software Reset	Current setting
	APM :
Power On Reset	C0h
Hardware Reset	Current setting
Software Reset	Current setting

30 Lyrion Series IDE Product Manual, Rev. B