AM79C971VCW Advanced Micro Devices, AM79C971VCW Datasheet - Page 240

• Manufacturer Part Number: AM79C971VCW
• Description: PCnet-FAST Single-Chip Full-Duplex 10/100 Mbps Ethernet Controller for PCI Local Bus
• Manufacturer: Advanced Micro Devices

D-4
N2: EOM
N0: Packet preamble, SFD
Ethernet
and destination address
are arriving.
activity:
Wire
{
N1: 64th byte of packet
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
C2: Controller writes descriptor #1.
C1: Controller is performing intermittent
C0: Lookahead to descriptor #2.
data arrives.
bursts of DMA to fill data buffer #3.
descriptor #3 (OWN).
bursts of DMA to fill data buffer #2.
is generated.
bursts of DMA to fill data buffer #1.
is generated.
}
}
Controller
Ethernet
activity:
Figure D1. LAPP Timeline
Am79C971
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-Etherenet
S6: Driver copies data from buffer #2 to the application buffer.
S5: Driver polls descriptor #2.
S4: Driver copies data from buffer #1 to the application buffer.
S1: Interrupt latency.
S0: Driver is idle.
application to run.
Software
activity:
} {
{
{
S7A: Driver Interrupt Service
S8: Driver calls application
S3: Driver writes modified application
S2: Driver call to application to
to tell application that
packet has arrived.
pointer to descriptor #3.
get application buffer pointer.
Routine executes
RETURN.
19364D-D1