FDC37M607 datasheet(103/182 Pages) SMSC

103 / 182 page

103

AUTO POWER MANAGEMENT

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 set, this bit allows FDC to enter

powerdown when all of the following conditions

have been met:

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.

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.

DSR From Powerdown

If DSR powerdown is used when the part is in

auto powerdown, the DSR powerdown will

override the auto powerdown. However, when

the part is 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. Besides activating the

RESET pin or one of the software reset bits in

the

DOR

DSR,

the

following

accesses will wake up the part:

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.

Once awake, the FDC will reinitiate the auto

powerdown timer for 10 ms.

The

part will

powerdown again when all the powerdown

conditions are satisfied.

FDC37M607 Datasheet(PDF) 103 Page - SMSC Corporation

FDC37M607 Datasheet(HTML) 103 Page - SMSC Corporation

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