AM79C976 Advanced Micro Devices, AM79C976 Datasheet - Page 82
![no-image](/images/manufacturer_photos/0/0/14/advanced_micro_devices_sml.jpg)
AM79C976
Manufacturer Part Number
AM79C976
Description
PCnet-PRO 10/100 Mbps PCI Ethernet Controller
Manufacturer
Advanced Micro Devices
Datasheet
1.AM79C976.pdf
(309 pages)
- Current page: 82 of 309
- Download datasheet (3Mb)
The receive process starts when RX_DV is asserted.
RX_DV must remain asserted until the end of the re-
ceive frame. If the external PHY device detects errors
in the currently received frame, it asserts the RX_ER
signal. RX_ER can be used to signal special conditions
out of band when RX_DV is not asserted. Two defined
out-of-band conditions for this are the 100BASE-TX
signaling of bad Start of Frame Delimiter and the
100BASE-T4 indication of illegal code group before the
receiver has synchronized with the incoming data. The
Am79C976 controller will not respond to these condi-
tions. All out of band conditions are currently treated as
NULL events. Certain in-band non-IEEE 802.3-compli-
ant flow control sequences may cause erratic behavior
for the Am79C976 controller. Consult the switch/
bridge/router/hub manual to disable the in-band flow
control sequences if they are being used.
The MII also provides the CRS (Carrier Sense) and
COL (Collision Sense) signals that are required for
IEEE 802.3 operation. Carrier Sense is used to detect
non-idle activity on the network for the purpose of inter-
frame spacing timing in half-duplex mode. Collision
Sense is used to indicate that simultaneous transmis-
sion has occurred in a half-duplex network.
The MII provides a two-wire management interface so
that the Am79C976 controller can control external PHY
devices and receive status from them.
The Am79C976 controller offers direct hardware sup-
port of the external PHY device without software inter-
vention. The device automatically uses the MII
Management Interface to read auto-negotiation infor-
mation from the external PHY device and configures
82
Am79C976
P R E L I M I N A R Y
Am79C976
the MAC accordingly. The controller also provides the
host CPU indirect access to the external PHY through
the MII Control, Address, and Data registers (BCR32,
33, 34).
With software support the Am79C976 controller can
support up to 31 external PHYs attached to the MII
Management Interface.
Two independent state machines use the MII Manage-
ment Interface to poll external PHY devices: the Net-
work Port Manager and the Auto-poll State Machine.
The Network Port Manager coordinates the auto-nego-
tiation process, while the Auto-poll State Machine inter-
rupts the host CPU when it detects changes in user-
selected PHY registers.
The Network Port Manager sends a management
frame to the default PHY about once every 900 ms to
determine auto-negotiation results and the current link
status. The Network Port Manager uses the auto-nego-
tiation results to set the MAC’s speed, duplex mode,
and flow control ability. Changes detected by the Net-
work Port Manager affect the operation of the MAC and
MIB counters. For example, if link failure is detected,
the transmitter will increment the XmtLossCarrier
counter each time it attempts to transmit a frame.
The Auto-poll State Machine periodically sends man-
agement frames to poll the status register of the default
PHY device plus up to 5 user-selected PHY registers
and interrupts the host processor if it detects a change
in any of these registers. The Auto-poll State Machine
does not change the state of the MAC engine.
The format of an MII Management Frame is defined in
Clause 22 of IEEE Std 802.3. The start of an MII Man-
4
4
RXD(3:0)
RX_DV
RX_ER
RX_CLK
CRS
COL
TXD(3:0)
TX_EN
TX_CLK
MDC
MDIO
Receive Signals
Network Status Signals
Management Port Signals
Transmit Signals
8/01/00
Related parts for AM79C976
Image
Part Number
Description
Manufacturer
Datasheet
Request
R
![AM27S29DC](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
Advanced Micro Devices [4,096-Bit (512x8) Bipolar PROM]
Manufacturer:
Advanced Micro Devices
Datasheet:
![AM27S29APC](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
Advanced Micro Devices [4,096-Bit (512x8) Bipolar PROM]
Manufacturer:
Advanced Micro Devices
Datasheet:
![AM29BL802CB-70RZE](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
Advanced Micro Devices [8 Megabit (512 K x 16-Bit) CMOS 3.0 Volt-only Burst Mode Flash Memory]
Manufacturer:
Advanced Micro Devices
Datasheet:
![M41000001Y](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
M41000001YAdvanced Micro Devices [32 Megabit (4 M x 8-Bit/2 M x 16-Bit) CMOS 3.0 Volt-only, Simultaneous Operation Flash Memory and 4 Mbit (512 K x 8-Bit/256 K x 16-Bit) Static RAM]
Manufacturer:
Advanced Micro Devices
Datasheet:
![AM95C94JC](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
Advanced Burst Error Processor
Manufacturer:
Advanced Micro Devices
![AM7992BPC](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
Serial interface adapter (SIA)
Manufacturer:
Advanced Micro Devices
Datasheet:
![AM9519ADC](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
Universal interrupt controller
Manufacturer:
Advanced Micro Devices
Datasheet:
![AM27C256-150DC](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
256 kilobit CMOS EPROM
Manufacturer:
Advanced Micro Devices
Datasheet:
![AM9128-10PC](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
2048 x 8 static RAM, 100ns
Manufacturer:
Advanced Micro Devices
Datasheet:
![P8284A](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
Manufacturer:
Advanced Micro Devices
Datasheet:
![DM81LS98N](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
Three-State Octal Buffers
Manufacturer:
Advanced Micro Devices
Datasheet:
![AM2966PC](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
AM2966PCOctal Dynamic Memory Drivers with Three-State Outputs
Manufacturer:
Advanced Micro Devices
Datasheet:
![DM81LS97N](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
Three-State Octal Buffers
Manufacturer:
Advanced Micro Devices
Datasheet:
![DM81LS96N](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
Three-State Octal Buffers
Manufacturer:
Advanced Micro Devices
Datasheet:
![PAL16L8-7PC](/images/manufacturer_photos/0/0/14/advanced_micro_devices_tmb.jpg)
Part Number:
Description:
TTL programmable array logic, 7ns
Manufacturer:
Advanced Micro Devices
Datasheet: