AM79C976 Advanced Micro Devices, AM79C976 Datasheet - Page 38

• Manufacturer Part Number: AM79C976
• Description: PCnet-PRO 10/100 Mbps PCI Ethernet Controller
• Manufacturer: Advanced Micro Devices

The Am79C976 controller does not support burst ac-
cess to the configuration space, the first 32 bytes of its
I/O or memory space, or to the Expansion Bus. The
host indicates a burst transaction by keeping FRAME
asserted during the data phase. When the Am79C976
controller sees FRAME and IRDY asserted in the clock
cycle before it wants to assert TRDY, it also asserts
STOP at the same time. The transfer of the first data
phase is still successful, since IRDY and TRDY are
both asserted. See Figure 66.
38
DEVSEL
FRAME
TRDY
STOP
C/BE
IRDY
CLK
PAR
AD
1
ADDR
CMD
2
PAR
3
DATA
BE
4
PAR
P R E L I M I N A R Y
5
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Am79C976
If the host is not yet ready when the Am79C976 control-
ler asserts TRDY, the device will wait for the host to as-
sert IRDY. When the host asserts IRDY and FRAME is
still asserted, the Am79C976 controller will finish the
first data phase by deasserting TRDY one clock later.
At the same time, it will assert STOP to signal a discon-
nect to the host. STOP will stay asserted until the host
removes FRAME. See Figure 77.
DEVSEL
FRAME
TRDY
STOP
IRDY
C/BE
CLK
PAR
AD
1
1st DATA
2
BE
PAR
3
DATA
BE
4
PAR
5
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