am79c974 Advanced Micro Devices, am79c974 Datasheet - Page 41

• Manufacturer Part Number: am79c974
• Description: Pcnettm-scsi Combination Ethernet And Scsi Controller For Pci Systems
• Manufacturer: Advanced Micro Devices

Preemption When FRAME is Asserted
The central arbiter can take GNT to the Am79C974 con-
troller away if the current bus operation takes too long.
This may happen, for example, when the Am79C974
controller tries to fill the whole Ethernet transmit FIFO
and the target inserts extra wait states for every data
phase. When GNT is taken away, the Am79C974 con-
DEVSEL
FRAME
TRDY
IRDY
C/BE
REQ
GNT
CLK
PAR
AD
1
DEVSEL is sampled by the Am79C974 controller.
Figure 15. Preemption When FRAME is Asserted
2
3
P R E L I M I N A R Y
ADDR
0111
4
Am79C974
DATA
PAR
5
0000
troller will finish the current transfer and then immedi-
ately release the bus. The Latency Timer in PCI
configuration space of the Am79C974 controller is al-
ways set to ZERO. The Am79C974 controller will keep
REQ asserted to regain bus ownership as soon as pos-
sible.
PAR
6
DATA
7
DATA
PAR
8
PAR
9
18681A-19
AMD
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