am79c970 Advanced Micro Devices, am79c970 Datasheet - Page 30

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

Master Initiated Termination
There are three scenarios besides normal completion of
a transaction where the PCnet-PCI controller will termi-
nate the cycles it produces on the PCI bus.
Preemption When FRAME is Deasserted
The PCnet-PCI controller will generate multiple address
phases during a single bus ownership period when it is
accessing the initialization block, the descriptor ring
DEVSEL
FRAME
TRDY
IRDY
C/BE
REQ
GNT
CLK
PAR
AD
Figure 10. Preemption When FRAME is Deasserted
1
DEVSEL is sampled by the PCnet-PCI controller.
2
P R E L I M I N A R Y
3
ADDR
0111
Am79C970
4
DATA
entries and the data buffers in main memory. FRAME is
deasserted in between two address phases. While
FRAME is deasserted, the central arbiter can remove
GNT to the PCnet-PCI controller at any time to service
another master. When GNT is removed, the PCnet-PCI
controller will finish the current transfer and then release
the bus. It will keep REQ asserted to regain bus owner-
ship as soon as possible.
BE's
PAR
5
PAR
6
7
8
18220C-12
AMD
1-897