AM79C976 Advanced Micro Devices, AM79C976 Datasheet - Page 99

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

Status, Receive Match, Receive Status, Magic Packet,
Transmit Status, and Start Frame/Byte Delimiter.
The LED pins can be configured to operate in either
open-drain mode (active low) or in totem-pole mode
(active high). The output can be stretched to allow the
human eye to recognize even short events that last only
several microseconds. After H_RESET, the four LED
outputs are configured as shown in Table 16.
For each LED register, each of the status signals is
AND’d with its enable signal, and these signals are all
OR’d together to form a combined status signal. Each
LED pin combined status signal can be programmed to
run to a pulse stretcher, which consists of a 3-bit shift
register clocked at 38 Hz (26 ms). The data input of
each shift register is normally at logic 0. The OR gate
output for each LED register asynchronously sets all
three bits of its shift register when the output becomes
asserted. The inverted output of each shift register is
used to control an LED pin. Thus, the pulse stretcher
provides 2 to 3 clocks of stretched LED output, or 52
ms to 78 ms. See Figure 4343.
8/01/00
Output
LED0
LED1
LED2
LED3
LED
Table 16. LED Default Configuration
Link Status
Indication
Activity
Speed
Coll
Driver Mode
Open Drain -
Open Drain -
Open Drain -
Open Drain -
Active Low
Active Low
Active Low
Active Low
Pulse Stretch
Enabled
Enabled
Enabled
Enabled
P R E L I M I N A R Y
Am79C976
B
Power Savings Mode
The Am79C976 controller supports power manage-
ment as defined in the PCI Bus Power Management In-
terface Specification V1.1 and Network Device Class
Power Management Reference Specification V1.0.
These specifications define the network device power
states, PCI power management interface including the
Capabilities Data Structure and power management
registers block definitions, power management events,
and OnNow network Wake-up events. In addition, the
Am79C976 controller supports legacy power manage-
ment schemes, such as Remote Wake-Up (RWU)
mode. The RWU mode can accommodate systems
that sleep with PCI bus power off or on and the PCI
clock running or stopped. The RWU pin can drive the
CPU's System Management Interrupt (SMI) line or a
system power controller.
The general scheme for the Am79C976 controller
power management is that when a wake-up event is
detected, a signal is generated to cause hardware ex-
ternal to the Am79C976 device to put the computer into
the working (S0) mode. The Am79C976 device sup-
ports three types of wake-up events:
The Am79C976 device supports two types of wake-up
control mechanisms:
MR_SPEED_SEL
RCVME
LNKSE
FDLSE
RCVM
RCVE
XMTE
MPSE
COLE
FDLS
LNKS
100E
RCV
XMT
MPS
COL
22929B-45
Pulse
Stretcher
To
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