am79c970 Advanced Micro Devices, am79c970 Datasheet - Page 27

• Manufacturer Part Number: am79c970
• Description: Pcnettm-pci Single-chip Ethernet Controller For Pci Local Bus
• Manufacturer: Advanced Micro Devices

Target Initiated Termination
When the PCnet-PCI controller is a bus master, the cy-
cles it produces on the PCI bus may be terminated by
the target in one of three different ways.
Disconnect With Data Transfer
Figure 7 shows a disconnection in which one last data
transfer occurs after the target asserted STOP. STOP is
asserted on clock 4 to start the termination sequence.
Data is still transferred during this cycles, since both
1-894
AMD
DEVSEL
FRAME
TRDY
STOP
IRDY
C/BE
REQ
GNT
CLK
PAR
AD
1
DEVSEL is sampled by the PCnet-PCI controller.
ADDR i
0111
2
DATA
PAR
Figure 7. Disconnect with Data Transfer
3
0000
DATA
PAR
4
P R E L I M I N A R Y
PAR
Am79C970
5
IRDY and TRDY are asserted. The PCnet-PCI control-
ler terminates the current transfer with the deassertion
of FRAME on clock 5 and then one clock cycle later with
the deassertion IRDY. It finally releases the bus on clock
6. The PCnet-PCI controller will re-request the bus after
2 clock cycles, if it wants to transfer more data. The
starting address of the new transfer will be the address
of the next untransferred data.
6
7
8
9
10
ADDR +8
0111
11
i
18220C-9