AM79C976 Advanced Micro Devices, AM79C976 Datasheet - Page 220

• Manufacturer Part Number: AM79C976
• Description: PCnet-PRO 10/100 Mbps PCI Ethernet Controller
• Manufacturer: Advanced Micro Devices

Bit
31-16
15-0
Note: Bits 15-0 in this register are programmable
through the EEPROM.
Bit
31-16
15-0
220
Name
RES
MIIMD
Name
RES
VID
5-bit Register Address field that is
used in the management frame
that gets clocked out via the MII
management port pins (MDC and
MDIO) whenever a read or write
transaction occurs to BCR34.
Read/Write accessible. REGAD
is undefined after H_RESET and
is unaffected by S_RESET and
the STOP bit.
zeros and read as undefined.
the data port for operations on
the MII management interface
(MDIO
Am79C976 device builds man-
agement frames using the PHY-
AD and REGAD values from
BCR33. The operation code used
in each frame is based upon
whether a read or write operation
has been performed to BCR34.
Read cycles on the MII manage-
ment interface are invoked when
BCR34 is read. Upon completion
of the read cycle, the 16-bit result
of the read operation is stored in
MIIMD. Write cycles on the MII
management interface are in-
voked when BCR34 is written.
The value written to MIIMD is the
value used in the data field of the
management write frame.
Read/Write accessible. MIIMD is
undefined after H_RESET and is
unaffected by S_RESET and the
STOP bit.
zeros and read as undefined.
register is a 16-bit register that
identifies the manufacturer of the
Am79C976
Reserved locations. Written as
MII Management Data. MIIMD is
Reserved locations. Written as
Vendor ID. The PCI Vendor ID
Description
Description
and
controller.
MDC).
P R E L I M I N A R Y
AMD’s
The
Am79C976
This register is an alias of the PMC register located at
offset 42h of the PCI Configuration Space. It is included
for compatibility with older PCnet devices. Since the
PMC register is read only, in older PCnet devices
BCR36 provides a means of programming PMC
through the EEPROM.
In the Am79C976 controller there is a single PMC reg-
ister that can be accessed through three different mem-
ory spaces. It can be accessed as read-only through
PCI Configuration Space (at offset 42h), read-only
through BCR36, or read-write through the memory-
mapped PMC Alias Register at offset 1B8h. It can be
loaded from the EEPROM through offset 1B8h in the
Am79C976 controller’s memory-mapped I/O space.
For the definition of the bits in this register, refer to the
PMC register definition. BCR36 is read only. It is set to
0C802h by H_RESET and is not affected by S_RESET
or setting the STOP bit.
The Vendor ID is not normally
programmable,
Am79C976 controller allows this
due to legacy operating systems
that do not look at the PCI Sub-
system Vendor ID and the Ven-
dor ID to uniquely identify the
add-in board or subsystem that
the Am79C976 controller is used
in.
Note: If the operating system or
the network operating system
supports PCI Subsystem Vendor
ID and Subsystem ID, use those
to identify the add-in board or
subsystem and program the VID
with the default value of 1022h.
VID is aliased to the PCI configu-
ration space register Vendor ID
(offset 00h).
VID is read only. Write operations
are ignored. VID is set to 1022h
by H_RESET and is not affected
by S_RESET or by setting the
STOP bit.
Vendor ID is 1022h. Note that this
Vendor ID is not the same as the
Manufacturer ID in CSR88 and
CSR89. The Vendor ID is as-
signed by the PCI Special Inter-
est Group.
but
8/01/00
the