am79c974 Advanced Micro Devices, am79c974 Datasheet - Page 42

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

Master Abort
The Am79C974 controller will terminate its cycle with a
Master Abort sequence if DEVSEL is not asserted within
4 clocks after FRAME is asserted. Master Abort is
treated as a fatal error by the Am79C974 controller. For
the Ethernet, the Am79C974 controller will reset all CSR
and BCR locations to their H_RESET values. Any
on-going network activity will be stopped immediately.
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AMD
DEVSEL
FRAME
TRDY
IRDY
C/BE
REQ
GNT
PAR
CLK
AD
1
DEVSEL is sampled by the Am79C974 controller.
2
3
ADDR
Figure 16. Master Abort
0111
P R E L I M I N A R Y
4
Am79C974
DATA
PAR
5
0000
The PCI configuration registers will not be cleared. For
SCSI, when the master aborts, INTA will not be as-
serted, but the ABORT bit (bit 2 of the DMA status regis-
ter at offset 54h), is set. For either Ethernet or SCSI
master abort causes RMABORT (bit 13) of the status
register in the appropriate PCI configuration space to
be set.
PAR
6
7
8
9
10
18681A-20