AM79C973BKC\W AMD (ADVANCED MICRO DEVICES), AM79C973BKC\W Datasheet - Page 109

• Manufacturer Part Number: AM79C973BKC\W
• Manufacturer: AMD (ADVANCED MICRO DEVICES)

Specifications of AM79C973BKC\W

• Operating Supply Voltage (typ): 3.3V
• Operating Supply Voltage (min): 3/3.135V
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 160
• Lead Free Status / RoHS Status: Not Compliant

I/O Resources
The Am79C973/Am79C975 controller requires 32
bytes of address space for access to all the various
internal registers as well as to some setup information
stored in an external serial EEPROM. A software reset
port is available, too.
The Am79C973/Am79C975 controller supports map-
ping the address space to both I/O and memory space.
The value in the PCI I/O Base Address register deter-
mines the start address of the I/O address space. The
register is typically programmed by the PCI configura-
tion utility
tion utility must also set the IOEN bit in the PCI
Command register to enable I/O accesses to the
Am79C973/Am79C975 controller. For memory mapped
I/O access, the PCI Memory Mapped I/O Base Address
register controls the start address of the memory space.
The MEMEN bit in the PCI Command register must also
be set to enable the mode. Both base address registers
can be active at the same time.
The Am79C973/Am79C975 controller supports two
modes for accessing the I/O resources. For backwards
compatibility with AMD’s 16-bit Ethernet controllers,
Word I/O is the default mode after power up. The device
can be configured to DWord I/O mode by software.
I/O Registers
The Am79C973/Am79C975 controller registers are di-
vided into two groups. The Control and Status Regis-
ters (CSR) are used to configure the Ethernet MAC
engine and to obtain status information. The Bus Con-
trol Registers (BCR) are used to configure the bus in-
terface unit and the LEDs. Both sets of registers are
accessed using indirect addressing.
The CSR and BCR share a common Register Address
Port (RAP). There are, however, separate data ports.
The Register Data Port (RDP) is used to access a
CSR. The BCR Data Port (BDP) is used to access a
BCR.
In order to access a particular CSR location, the RAP
should first be written with the appropriate CSR ad-
dress. The RDP will then point to the selected CSR. A
read of the RDP will yield the selected CSR data. A
write to the RDP will write to the selected CSR. In order
to access a particular BCR location, the RAP should
first be written with the appropriate BCR address. The
BDP will then point to the selected BCR. A read of the
BDP will yield the selected BCR data. A write to the
BDP will write to the selected BCR.
Once the RAP has been written with a value, the RAP
value remains unchanged until another RAP write oc-
curs, or until an H_RESET or S_RESET occurs. RAP
is cleared to all 0s when an H_RESET or S_RESET oc-
curs. RAP is unaffected by setting the STOP bit.
after system power-up. The PCI configura-
P R E L I M I N A R Y
Am79C973/Am79C975
Address PROM Space
The Am79C973/Am79C975 controller allows for con-
nection of a serial EEPROM. The first 16 bytes of the
EEPROM will be automatically loaded into the Address
PROM (APROM) space after H_RESET. Additionally,
the first six bytes of the EEPROM will be loaded into
CSR12 to CSR14. The Address PROM space is a con-
venient place to store the value of the 48-bit IEEE sta-
tion address. It can be overwritten by the host computer
and its content has no effect on the operation of the
controller. The software must copy the station address
from the Address PROM space to the initialization
block in order for the receiver to accept unicast frames
directed to this station.
The six bytes of the IEEE station address occupy the
first six locations of the Address PROM space. The
next six bytes are reserved. Bytes 12 and 13 should
match the value of the checksum of bytes 1 through 11
and 14 and 15. Bytes 14 and 15 should each be ASCII
“W” (57h). The above requirements must be met in
order to be compatible with AMD driver software.
APROMWE bit (BCR2, bit 8) must be set to 1 to enable
write access to the Address PROM space.
Reset Register
A read of the Reset register creates an internal soft-
ware reset (S_RESET) pulse in the Am79C973/
Am79C975 controller. The internal S_RESET pulse
that is generated by this access is different from both
the assertion of the hardware RST pin (H_RESET) and
from the assertion of the software STOP bit. Specifi-
cally, S_RESET is the equivalent of the assertion of the
RST pin (H_RESET) except that S_RESET has no ef-
fect on the BCR or PCI Configuration space locations.
The NE2100 LANCE-based family of Ethernet cards
requires that a write access to the Reset register fol-
lows each read access to the Reset register. The
Am79C973/Am79C975 controller does not have a sim-
ilar requirement. The write access is not required and
does not have any effect.
Note: The Am79C973/Am79C975 controller cannot
service any slave accesses for a very short time after a
read access of the Reset register, because the internal
S_RESET operation takes about 1 ms to finish. The
Am79C973/Am79C975 controller will terminate all
slave accesses with the assertion of DEVSEL and
STOP while TRDY is not asserted, signaling to the ini-
tiator to disconnect and retry the access at a later time.
Word I/O Mode
After H_RESET, the Am79C973/Am79C975 controller
is programmed to operate in Word I/O mode. DWIO
(BCR18, bit 7) will be cleared to 0. Table 20 shows how
the 32 bytes of address space are used in Word I/O
mode.
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