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AM79C976 Datasheet PDF : 309 Pages
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PRELIMINARY
GENERAL DESCRIPTION
The Am79C976 controller is a highly-integrated 32-bit
full-duplex, 10/100-Megabit per second (Mbps) Ether-
net controller solution, designed to address high-
performance system application requirements. It is a
flexible bus mastering device that can be used in any
application, including network-ready PCs and bridge/
router designs. The bus master architecture provides
high data throughput and low CPU and system bus uti-
lization. The Am79C976 controller is fabricated with
advanced low-power 3.3-V CMOS process to provide
low operating current for power sensitive applications.
The Am79C976 controller also has several enhance-
ments over its predecessor, the Am79C971
PCnet-FAST device. In addition to providing access to
a larger SSRAM, it further reduces system implemen-
tation cost by the addition of a new EEPROM program-
mable pin (PHY_RST) and the integration of the PAL
function needed for Magic Packet application. The
PHY_RST pin is implemented to reset the external
PHY without increasing the load to the PCI bus and to
block RST to the PHY when PG input is LOW.
The 32-bit multiplexed bus interface unit provides a di-
rect interface to the PCI local bus, simplifying the de-
sign of an Ethernet node in a PC system. The
Am79C976 controller provides the complete interface
to an Expansion ROM or Flash device allowing add-on
card designs with only a single load per PCI bus inter-
face pin. With its built-in support for both little and big
endian byte alignment, this controller also addresses
non-PC applications. The Am79C976 controller’s
advanced CMOS design allows the bus interface to be
connected to either a +5-V or a +3.3-V signaling envi-
ronment. An IEEE 1149.1-compliant JTAG test inter-
face for board-level testing is also provided.
The Am79C976 controller is also compliant with the
PC97, PC98, PC99, and Network PC (Net PC) specifi-
cations. It includes the full implementation of the Mi-
crosoft OnNow and ACPI specifications, which are
backward compatible with the Magic Packet technol-
ogy, and it is compliant with the PCI Bus Power Man-
agement Interface Specification by supporting the four
power management states (D0, D1, D2, and D3), the
optional PME pin, and the necessary configuration and
data registers.
The Am79C976 controller is ideally suited for Net PC,
motherboard, network interface card (NIC), and em-
bedded designs. It is available in a 208-pin Plastic
Quad Flat Pack (PQFP) package.
The Am79C976 controller contains a bus interface unit,
a DMA Buffer Management Unit, an ISO/IEC 8802-3
(IEEE 802.3)-compliant Media Access Controller
(MAC), and an IEEE 802.3-compliant MII. An interface
to an external RAM of up to 4 Mbytes is provided for
frame storage. The MII supports IEEE 802.3-compliant
full-duplex and half-duplex operations at 10 Mbps or
100 Mbps. The MII TX and RX clock signals can be
stopped independently for home networking applica-
tions.
The Am79C976 controller is register compatible with
the LANCE™ (Am7990) and C-LANCE™ (Am79C90)
Ethernet controllers, and all Ethernet controllers in the
PCnet Family except ILACC™ (Am79C900), including
the PCnet™-ISA controller (Am79C960),
PCnet™-ISA+ (Am79C961), PCnet™-ISA II
(Am79C961A), PCnet™-32 (Am79C965), PCnet™-
PCI (Am79C970), PCnet™-PCI II (Am79C970A), and
the PCnet™-FAST (Am79C971).
The Buffer Management Unit supports the LANCE and
PCnet descriptor software models.
The Am79C976 controller supports auto-configuration
in the PCI configuration space. Additional Am79C976
controller configuration parameters, including the
unique IEEE physical address, can be read from an ex-
ternal nonvolatile memory (EEPROM) immediately fol-
lowing system reset.
In addition, the device provides programmable on-chip
LED drivers for transmit, receive, collision, link integrity,
Magic Packet status, activity, address match, full-
duplex, or 100 Mbps status. The Am79C976 controller
also provides an EADI to allow external hardware ad-
dress filtering in internetworking applications and a
receive frame tagging feature.
With the rise of embedded networking applications op-
erating in harsh environments where temperatures
may exceed the normal commercial temperature (0 C
to +70 C) window, an industrial temperature (-40 C to
+85 C) version is available. This industrial temperature
version of the PCnet-PRO Ethernet controller is char-
acterized across the industrial temperature range (-40
C to +85 C) within the published power supply specifi-
cation (4.75V to 5.25V; ±5% Vcc). Thus, conformance
of the PCnet-PRO performance over this temperature
range is guaranteed by a design and characterization
monitor.
8/01/00
Am79C976
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