30 Lyrion Series IDE Product Manual, Rev. B
4.2.2 Set 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
The following drive features are set after a Power On Reset, Hardware Reset or Software Reset.
Transfer mode : Write Cache :
Power On Reset PIO 4, MDMA 2 Power On Reset Enabled
Hardware Reset PIO 4, MDMA 2 Hardware Reset Enabled
Software Reset Current setting Software Reset Current setting
Read look-ahead : APM :
Power On Reset Enabled Power On Reset C0h
Hardware Reset Enabled Hardware Reset Current setting
Software Reset Current setting Software Reset Current setting
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 .