DP83256 datasheet(35/146 Pages) TI1

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40 Modes of Operation (Continued)

44 DEVICE RESET

The revision B PLAYERa device has five different levels of

device ResetPower 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 PLAYERa device and reaches a certain volt-

age level Power Up Reset affects all of the modules in the

PLAYERa device specifically the Clock Generation Mod-

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 PLAYERa device is reset This reset takes the longest

amount of time at approximately 10 ms from the time the

PLAYERa device’s power supply reaches 44V

Even

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 PLAYERa after waiting a mini-

mum of 10 ms for the Power Up Reset to complete its reset

attempt

Hardware Reset occurs at the rising edge of PLAYERa

device’s ERST pin Hardware Reset affects all of the mod-

ules in the PLAYERa device specifically the CGM CRM

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 ERST

Player Reset is activated by writinga1tothe PHYRST bit in

Mode Register 2 Player Reset only affects the Player Mod-

ule This reset is the shortest and only takes about 3 ms

from the completion of the register write The device should

not be accessed by the Control Bus during this reset

Reference Select Reset occurs when the PLAYERa de-

vice’s REF

SEL pin is switched from using the REF

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 writinga0totheRUNbitinthe

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 PLAYERa device Two changes were made to

the original revision A PLAYERa device reset logic

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 PLAYERa device

has already waited for the crystal to settle once during the

Power Up Reset The revision A PLAYERa follows a Power

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 PLAYERa

Recommendations

The following are some recommendations for using the re-

set mechanisms of the PLAYERa most effectively

1 Always wait a minimum of 10 ms after power-up before

doing anything to the PLAYERa device 10 ms is a mini-

mum

it may be desirable to wait longer if the system

power supply or clock reference has not stabilized by this

time

2 Always use the Hardware Reset to reset the PLAYERa

device after Power Up This should be done after the

initial Power Up waiting period of at least 10 ms

DP83256 Datasheet(PDF) 35 Page - Texas Instruments

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