AM79C971VCW Advanced Micro Devices, AM79C971VCW Datasheet - Page 247

• Manufacturer Part Number: AM79C971VCW
• Description: PCnet-FAST Single-Chip Full-Duplex 10/100 Mbps Ethernet Controller for PCI Local Bus
• Manufacturer: Advanced Micro Devices

Auto-Negotiation Registers
The following registers exist in the Auto-Negotiation
block and are written or read by using registers MII Ad-
dress (BCR33) and MII Data Port (BCR34). These reg-
isters are indirect read and write registers with the
register offset specified by the REGAD (BCR33, bits 3-
0) portion of the MII Address Register (BCR33). The
PHYAD (BCR33, bits 3-0) portion specifies the specific
PHY that you wish to communicate with. The internal
PHY on the Am79c971 controller has a PHYAD ad-
dress of 1fh. The default external PHY has a PHYAD
address of 00h. The following is a table of these indirect
registers and defaulted values for the internal registers.
Register 0: MII Control Register
Bit
15
14
* See text on Auto Negotiation.
Name
PRPHY
LB
APPENDIX E
Default
Reset.
NA (0)
Description
Defaults
after power-up and
after hardware resets
(H_RESET). This is
normally only used to
bring up the external
PHY into a known
state. Not used for the
internal PHY. Use the
normal
reset mechanisms.
Loop Back. Defaults
to ZERO after power-
up and after hardware
resets
Loopback
supported only in an
external PHY. See
the
Configuration”
section
details..
(H_RESET).
Am79C971
for
to
ZERO
more
“MII
Am79C971
is
13
12
11
SS
ANE
PD
NA (0)
Variable*
NA (0)
Speed
Defaults
after power-up and
after hardware resets
(H_RESET). This is
ZERO the entire time
the internal PHY is
active. The external
PHY can be forced
into
10Mbps
manipulation of this
bit. This bit is used
only when the Auto-
Negotiation
bit is ZERO.
Auto-Negotiation
Enable. Defaults to
ONE after power-up
and after hardware
resets
This bit enables the
internal or external
PHY’s
Negotiation
capabilities.
this bit is ZERO the
internal/external
PHY’s must be forced
into the correct state
through
intervention.
Power
Defaults
after power-up and
after hardware resets
(H_RESET). This bit
only applies to the
external PHY. Use
the SLEEP# or other
power saving modes
in
Controller.
the
100Mbps
(H_RESET).
Am79C971
mode
to
to
Selection.
software
Enable
Down.
ZERO
ZERO
When
Auto-
E-1
by
or