CLK
1
2
3
4
5
6
7
8
9
10
11
FRAME
DATA
ADDR
0111
AD
C/BE
BE
PAR
PAR
PAR
IRDY
TRDY
DEVSEL
STOP
22206B-9
Figure 6. Slave Write Using Memory Command
pansion ROM is present when it reads the ROM signa-
ture 55H (byte 0) and AAH (byte 1).
Expansion ROM Transfers
Since the Am79C978 device does not have expansion
ROM capabilities, PCI configuration offset must be set
to 30H = 0.
Slave Cycle Termination
There are three scenarios besides normal completion
of a transaction where the Am79C978 controller is the
target of a slave cycle and it will terminate the access.
During the boot procedure, the system will try to find an
Expansion ROM. A PCI system assumes that an Ex-
CLK
1
2
3
4
5
48
49
50
51
FRAME
ADDR
CMD
DATA
AD
C/BE
PAR
BE
PAR
PAR
IRDY
TRDY
DEVSEL
STOP
22206B-10
DEVSEL is sampled
Figure 7. Expansion ROM Read
Am79C978
39
AMD [ AMD ]
