DP83861VQM Datasheet, PDF (86/88 Pages) National Semiconductor (TI) – Gig PHYTER 10/100/1000 Ethernet Physical Layer

— 7) Write 0x8400 to register 0x1F. This starts execution of
down loaded code at address 0x8400.
— 8)Wait for 1.024 ms. (i.e. no MDC/MDIO access for
1.024 ms)
— 9) Read register 0x00 (This read is needed to clear an in-
terrupt problem.)
— 10) Take the EN Gig PHYTER out of power down mode
(i.e. reset bit 11 of register 0x00.)
8.15 Q15: How is the maximum junction tempera-
ture calculated?
A15: The maximum die temperature is calculated using the
following equations:
T_J = T_A + P_d(Θ_JA)
T_J = T_C + P_d(Θ_JC)
T_C = T_J - P_d(Θ_JC)
8.10 Q10: How long does Auto-Negotiation take?
A10: Two EN Gig PHYTERs typically complete Auto-Nego-
tiation and establish 1000 Mb/s operation within 5 seconds.
1000BASE-T Auto-Negotiation process takes longer than
the 10/100 Mb/s. One of the reasons for this is the use of
Next Page exchanges during 1000 Mb/s negotiation.
8.11 Q11: I know I have good link, but register
0x01, bit 2 “Link Status” doesn’t contain value =
‘1’ indicating good link.
A11: This bit is defined by IEEE 802.3u Clause 22. It indi-
cates if the link was lost since the last time this register was
read. Its name (given by IEEE) is perhaps misleading. A
more accurate name would have been the “Link lost” bit. If
the actual present link status is desired, then either this
register should be read twice, or register 0x11 bit 2 should
be read. Register 0x11 shows the actual status of link,
speed, and duplex regardless of what was advertised or
what has happened in the interim.
8.12 Q12: I have forced 100 Mb/s operation but
the 100 Mb/s speed LED doesn’t come on.
A12: Speed LEDs are actually an AND function of the
speed and link status. Regardless of whether the speed is
forced or Auto-Negotiated, there has to be good link,
before the speed LEDs will come on.
Where:
T_J
T_C
= Junction temperature of
= Case temperature of the
the die in ^oC
package in ^oC
P_d
Θ_JA
Θ_JC
=
=
Power dissipated
11.7 ^oC/watt
= 2.13 ^oC/watt
in
the
die
in
Watts
For reliability purposes the maximum junction should be
kept below 120 ^oC. If the Ambient temperature is 70 ^oC
and the power dissipation is 4.0 watts then the Maximum
Case Temperature will be:
T_{C max} = 120 ^oC - 4.0 watts(2.13 ^oC/watt)
T_{C max} = 111.48 ^oC
8.16 Q16: How do I measure FLP’s?
A16: In order measure FLP’s you must first disable Auto
MDIX function. When in Auto MDIX mode the DP83861 will
put out link pulses every 150 µs. The MDIX pulse could be
confused with the FLP pulses which occur every 125 µs +/-
14 µs.
To disable MDIX the following register writes need to be
done
8.13 Q13: Your reference design shows pull-up or
pull-down resistors attached to certain pins,
which conflict with the pull-up or pull-down infor-
mation specified in the datasheet?
Reg- Write
ister
Comments
0x00 bit 11 = 1 This puts the DP83861 into power down
mode.
A13: The pull-up or pull-down information specified in the
pin description section of the datasheet, indicate if there is
an internal pull-up or pull-down resistor at the IO buffer
used for that specific pin. These internal resistors are
between 25 - 65 kΩ. They will determine the default strap
value if the pin is floated. If the default value is desired to
be overwritten, then an external 2 KΩ pull-up or pull-down
resistor can be used.
0x16 000D This allows access to expanded memory
mode.
0x1E 808B This allows access to expanded memory
808B.
0x1D 0001 This disables MDIX mode.
0x00 bit 11 = 0 This takes the DP83861 out of power
down mode.
8.14 Q14: What are some other applicable docu-
ments?
A14:
Once MDIX is disabled the DP83861 will randomly come
up in cross over mode or straight cable mode output FLP’s
on either pins 1 and 2 or 3 and 6 on the RJ45.
— DP83861 Reference Design (Schematics, BOM, Gerber
files.)
— IEEE 802.3z “MAC Parameters, Physical Layer, Repeat-
er and Management Parameters for 1000 Mb/s Opera-
tion.”
— IEEE 802.3ab “Physical layer specification for 1000 Mb/s
operation on four pairs of category 5 or better balanced
twisted pair cable (1000BASE-T)“.
— IEEE 802.3 and 802.3u (For 10/100 Mb/s operation.)
8.17 Q17: The DP83861 will establish Link in 10
Mb/s and 100Mb/s mode with a Broadcom part,
but it will not establish link in 1000 Mb/s mode.
When this happens the DP83861’s Link led will
blink on and off.
A17: We have received a number of questions regarding
inter-operability of National’s DP83861 with Broadcom’s
BCM5400. National’s DP83861 is compliant to IEEE
802.3ab and it is also inter-operable with the BCM5400 as
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