am79c974 Advanced Micro Devices, am79c974 Datasheet - Page 34

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

Basic Non-Burst Write
All Am79C974 controller non-burst write accesses are
of the PCI command type Memory Write (type 7).
Figure 8 shows two non-burst write access within one
arbitration cycle. The Am79C974 controller will drop
FRAME between two consecutive non-burst write cy-
cles. The Am79C974 controller will re-request the bus
34
DEVSEL
FRAME
AMD
TRDY
IRDY
C/BE
REQ
GNT
PAR
CLK
AD
1
DEVSEL is sampled by the Am79C974 controller.
Figure 8. Non-Burst Write Cycles With and Without Wait States
2
3
ADDR
0111
4
P R E L I M I N A R Y
DATA
BE's
PAR
5
Am79C974
PAR
6
immediately if it is preempted before starting the second
access. The example below shows an extended cycle
for the first access. The target asserts DEVSEL 2 clock
cycles after the address phase (FRAME asserted) and
adds one extra wait state by asserting TRDY only on
clock 7. The second write cycle in the example shows a
ZERO wait state access.
7
8
ADDR
0111
9
DATA
BE's
PAR
10
PAR
11
18681A-12