AM79C976 Advanced Micro Devices, AM79C976 Datasheet - Page 294

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

A-9
N2:EOM
Ethernet
N0: Packet preamble, SFD
activity:
Wire
and destination address
are arriving.
C10: ERP interrupt
C9: Controller writes descriptor #3.
C8: Controller is performing intermittent
C7: Controller writes descriptor #2.
C6: "Last chance" lookahead to
C5: Controller is performing intermittent
C4: Lookahead to descriptor #3 (OWN).
C3: SRP interrupt is
C2: Controller writes descriptor #1.
C1: Controller is performing intermittent
C0: Lookahead to descriptor #2.
bursts of DMA to fill data buffer #3.
descriptor #3 (OWN).
bursts of DMA to fill data buffer #
generated.
bursts of DMA to fill data buffer #1
{
is generated.
N1: 64th byte of packet
data arrives.
}
}
Controller
Ethernet
activity:
P R E L I M I N A R Y
2
.
Am79C976
Buffer
Buffer
Buffer
#3
#2
#1
S10: Driver sets up TX descriptor.
S9: Application processes packet, generates TX packet.
S8A: Interrupt latency.
S7: Driver is swapped out, allowing a non-Ethernet
S6: Driver copies data from buffer #2 to the application
S5: Driver polls descriptor #2.
S4: Driver copies data from buffer #1 to the application
S1: Interrupt latency.
S0: Driver is idle.
application to run.
buffer.
buffer.
Software
activity:
}
}
S3: Driver writes modified application
S2: Driver call to application to
pointer to descriptor #3.
get application buffer pointer.
}
}
S8: Driver calls application
S 7A: Driver Interrupt Service
to tell application that
packet has arrived.
Routine executes
RETURN.
8/01/00
D-3