FDC37C78-HT Standard Microsystems (SMSC), FDC37C78-HT Datasheet - Page 59

• Manufacturer Part Number: FDC37C78-HT
• Manufacturer: Standard Microsystems (SMSC)

Specifications of FDC37C78-HT

• Package Type: TQFP
• Lead Free Status / RoHS Status: Compliant

Once awake, the FDC37C78 will reinitiate the
auto powerdown timer for 10 ms. The part will
powerdown again when all the powerdown
conditions are satisfied.
Register Behavior
Table 30 reiterates the AT registers available. It
also shows the type of access permitted. In order
to maintain software transparency, access to all
the registers must be maintained. As Table 30
shows, two sets of registers are distinguished
based on whether their access results in the part
remaining in powerdown state or exiting it.
Access to all other registers is possible without
awakening the part.
accessed during powerdown without changing the
status of the part. A read from these registers will
reflect the true status as shown in the register
description in the FDC description. A write to the
part will result in the part retaining the data and
subsequently reflecting it when the part awakens.
Accessing the part during powerdown may cause
an increase in the power consumption by the
part. The part will revert back to its low power
mode when the access has been completed.
These registers can be
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Pin Behavior
The FDC37C78 is
portable PC systems in which power conservation
is a primary concern. This makes the behavior of
the pins during powerdown very important.
The pins of the FDC37C78 can be divided into
two major categories: system interface and floppy
disk drive interface. The floppy disk drive pins are
disabled so that no power will be drawn through
the part as a result of any voltage applied to the
pin within the part's power supply range. Most of
the system interface pins are left active to monitor
system accesses that may wake up the part.
System Interface Pins
Table 31 gives the state of the system interface
pins in the powerdown state. Pins unaffected by
the powerdown are labeled "Unchanged". Input
pins are "Disabled" to prevent them from causing
currents internal to the FDC37C78 when they have
indeterminate input values.
specifically
designed
for