FDC37M81x SMSC Corporation, FDC37M81x Datasheet - Page 106

• Manufacturer Part Number: FDC37M81x
• Description: PC98/99 Compliant Enhanced Super I/O Controller
• Manufacturer: SMSC Corporation

Power management capabilities are provided for
the following logical devices: floppy disk, UART 1,
UART 2 and the parallel port. For each logical
device, two types of power management are
provided; direct powerdown and auto powerdown.
FDC Power Management
Direct power management is controlled by CR22.
Refer to CR22 for more information.
Auto Power Management is enabled by CR23-B0.
when all of the following conditions have been met:
1.
2.
3.
4.
An internal timer is initiated as soon as the auto
powerdown command is enabled. The part is then
powered down when all the conditions are met.
Disabling the auto powerdown mode cancels the
timer and holds the FDC block out of auto
powerdown.
When set, this bit allows FDC to enter powerdown
The motor enable pins of register 3F2H are
inactive (zero).
The part must be idle; MSR=80H and INT = 0
(INT may be high even if MSR = 80H due to
polling interrupts).
The head unload timer must have expired.
The Auto powerdown timer (10msec) must
have timed out.
POWER MANAGEMENT
106
DSR From Powerdown
If DSR powerdown is used when the part is in auto
powerdown, the DSR powerdown will override the
auto powerdown.
awakened from DSR powerdown, the auto
powerdown will once again become effective.
Wake Up From Auto Powerdown
If the part enters the powerdown state through the
auto powerdown mode, then the part can be
awakened by reset or by appropriate access to
certain registers.
If a hardware or software reset is used then the
part will go through the normal reset sequence. If
the access is through the selected registers, then
the FDC resumes operation as though it was
never in powerdown.
RESET_DRV pin or one of the software reset bits
in the DOR or DSR, the following register
accesses will wake up the part:
1.
2.
3.
Once awake, the FDC will reinitiate the auto
powerdown timer for 10 ms.
powerdown again when all the powerdown
conditions are satisfied.
Enabling any one of the motor enable bits in
the DOR register (reading the DOR does not
awaken the part).
A read from the MSR register.
A read or write to the Data register.
However, when the part is
Besides activating the
The
part will