am79c970 Advanced Micro Devices, am79c970 Datasheet - Page 157

• Manufacturer Part Number: am79c970
• Description: Pcnettm-pci Single-chip Ethernet Controller For Pci Local Bus
• Manufacturer: Advanced Micro Devices

C7: After filling the second buffer and performing the
S6: After the ownership of descriptor number 2 has
C8: The PCnet-PCI controller will perform data DMA
1-1024
AMD
last chance lookahead to the next descriptor, the
PCnet-PCI controller will write the status and
change the ownership bit of descriptor number 2.
been changed by the PCnet-PCI controller, the
next driver poll of the 2nd descriptor will show
ownership granted to the CPU. The driver now
copies the data from buffer number 2 into the mid-
dle section of the application buffer space. This
operation is interleaved with the C7 and C8
operations.
to the last buffer, whose pointer is pointing to ap-
plication space. Data entering the last buffer will
not need the infamous double copy that is required
by existing drivers, since it is being placed directly
into the application buffer space.
Am79C970
N2: The message on the wire ends.
S7: When the driver completes the copy of buffer
C9: When the PCnet-PCI controller has finished all
S8: The driver sees that the ownership of descriptor
S9: The application processes the received frame and
S10: The driver sets up the TX descriptor for the
number 2 data to the application buffer space, it
begins polling descriptor number 3.
data DMA operations, it writes status and changes
ownership of descriptor number 3.
number 3 has changed, and it calls the application
to tell the application that a frame has arrived.
generates the next TX frame, placing it into a TX
buffer.
PCnet-PCI controller.