AT INTERFACE and ATA COMMANDS
WA31273A / WA32543A / WA33203A / WA32163A / WA31083A / WA32162A 6-29
6-4-5 Idle (97h,E3h)
This command causes the drive to set BSY, enter the Idle Mode, clear BSY, and generate
an interrupt. The interrupt is generated even though the drive may not have fully
transitioned to Idle Mode.
If the drive is already spinning, the spin-up sequence is not executed.
If the Sector Count Register is non-zero, the automatic Idle Mode sequence is enabled
and the timer begins counting down immediately. If the Sector Count Register is zero,
the automatic power down sequence is disabled.
After the drive entered the Idle Mode, it automatically transitions to the Standby Mode
upon expiration of a prescribed 1 minute spin-down timer.
Table 6-7.
Automatic Standby Timer Periods
Sector Count Register Contents
Corresponding Time-out Period
0 (00h)
Timeout Disabled
1-240 (01h-FOh)
(value * 5) seconds
241-251 (F1h-FBh)
((value - 240) * 30) minutes
252 (FCh)
21 minutes
253 (FDh)
8 hours
254 (FEh)
Reserved
255 (FFh)
21 minutes 15 seconds
6-4-6 Idle Immediate (95h,E1h)
This command causes the drive to set BSY, enter the Idle Mode, clear BSY, and generate
an interrupt. The interrupt is generated even though the drive may not have fully
transitioned to Idle Mode.
6-4-7 Initialize Device Parameters (91h)
This command enables the host to set the number of sectors per track and the number of
heads minus 1, per cylinder. Upon receipt of the command, the drive sets BSY, saves the
parameters, clears BSY, and generates an interrupt.
The only two register values used by this command are the Sector Count Register which
specifies the number of sectors per track, and the Drive/Head Register which specifies
the number of heads minus 1. The DRV bit designates these values to Drive 0 or Drive 1,
as appropriate.
