DP83257VF National Semiconductor, DP83257VF Datasheet - Page 34

• Manufacturer Part Number: DP83257VF
• Description: IC FDDI LAYER CTRLR 160PQFP
• Manufacturer: National Semiconductor

Specifications of DP83257VF

• Controller Type: physical layer controller
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 160-BFQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Supply: -
• Interface: -
• Other names: *DP83257VF

4 0 Modes of Operation
4 4 DEVICE RESET
The revision B PLAYER
device Reset Power Up Reset Hardware Reset Player
Reset Reference Select Reset and Stop Mode The Re-
sets can be used to return the whole device or a portion of
the device to its default configuration
Power Up Reset begins automatically when power is first
applied to the PLAYER
age level Power Up Reset affects all of the modules in the
PLAYER
ule (CGM) Clock Recovery Module (CRM) and the Player
Module returning each module to its default configuration
This reset begins by waiting for the crystal to stabilize then
the CGM PLL proceeds to lock to the crystal and the rest of
the PLAYER
amount of time at approximately 10 ms from the time the
PLAYER
though the Power Up Reset is usually effective due to the
variation in the start-up conditions of a systems power sup-
ply the Power Up Reset trigger can not be guaranteed to
operate correctly Therefore a Hardware Reset should al-
ways be performed on the PLAYER
mum of 10 ms for the Power Up Reset to complete its reset
attempt
Hardware Reset occurs at the rising edge of PLAYER
device’s E RST pin Hardware Reset affects all of the mod-
ules in the PLAYER
and the Player Module returning each module to its default
configuration During Hardware Reset it is not necessary to
force the Clock Generation Module to wait for the crystal to
settle again at this time because it has settled in the time
since the initial reset at power up This reset takes the sec-
ond longest amount of time at approximately 1 ms from the
rising edge of E RST
Player Reset is activated by writing a 1 to the PHYRST bit in
Mode Register 2 Player Reset only affects the Player Mod-
ule This reset is the shortest and only takes about 3
from the completion of the register write The device should
not be accessed by the Control Bus during this reset
a
a
device specifically the Clock Generation Mod-
a
device’s power supply reaches 4 4V Even
device is reset This reset takes the longest
a
a
a
device specifically the CGM CRM
device and reaches a certain volt-
device has five different levels of
a
after waiting a mini-
(Continued)
a
s
34
Reference Select Reset occurs when the PLAYER
vice’s REF SEL pin is switched from using the REF IN
input to using a crystal with the XTAL IN and XTAL OUT
pins This is the same as a Power Up Reset and is done
because the crystal is going from a dead stop to an active
state when REF SEL is switched This reset like the Pow-
er Up Reset takes about 10 ms from the falling edge of
REF SEL
Stop Mode is activated by writing a 0 to the RUN bit in the
Mode Register Stop Mode is a selective reset that resets
the Clock Recovery Module and portions of the Player Mod-
ule
Changes from Revision A to Revision B
The previous descriptions describe the reset logic in the
revision B PLAYER
the original revision A PLAYER
First the Hardware Reset was shortened by eliminating the
requirement of having to wait for the crystal to settle before
letting the Clock Generation Module try to lock to the crys-
tal This behavior is correct because the PLAYER
has already waited for the crystal to settle once during the
Power Up Reset The revision A PLAYER
Up Reset cycle when Hardware Reset is activated
Second a full Power Up Reset is now done when the clock
reference is switched to the crystal This is necessary to
allow the crystal time to start up when it is switched to from
the REF IN input This reset is not performed on the revi-
sion A PLAYER
Recommendations
The following are some recommendations for using the re-
set mechanisms of the PLAYER
1 Always wait a minimum of 10 ms after power-up before
2 Always use the Hardware Reset to reset the PLAYER
doing anything to the PLAYER
mum it may be desirable to wait longer if the system
power supply or clock reference has not stabilized by this
time
device after Power Up This should be done after the
initial Power Up waiting period of at least 10 ms
a
a
device Two changes were made to
a
a
a
device reset logic
most effectively
device 10 ms is a mini-
a
follows a Power
a
a
device
de-
a