DS495 Datasheet, PDF (9/12 Pages) Xilinx, Inc – PCI Arbiter

PCI Arbiter (v1.00a)
Figure 8 is another example of the PCI_Arbiter operation for multiple requests. Initially the park
master is number two and all six connected master agents requests access simultaneously. The
PCI_Arbiter sequentially grants access to agents three through five then provides access to master
agents zero, one and two in order. As master agent two is the last active master, it completes this
example as the park master.
Figure Top x-ref 8
pci_clk
pci_rst_n
pci_req_n(0)
pci_req_n(1)
pci_req_n(2)
pci_req_n(3)
pci_req_n(4)
pci_req_n(5)
pci_frame
pci_irdy_n
pci_gnt_n(0)
pci_gnt_n(1)
pci_gnt_n(2)
pci_gnt_n(3)
pci_gnt_n(4)
pci_gnt_n(5)
Figure 8: PCI_Arbiter Response to Multiple Requests
X495_08_101306
Figure 9 shows the situation of a master agent, number two, requesting access, as another agent,
number three also requests access. After agent number two fails to respond, the PCI_Arbiter grants
access to the second requesting agent, number three. Agent number three then becomes the last active
master and the park master.
Figure Top x-ref 9
pci_clk
pci_rst_n
pci_req_n(0)
pci_req_n(1)
pci_req_n(2)
pci_req_n(3)
pci_req_n(4)
pci_req_n(5)
pci_frame
pci_irdy_n
pci_gnt_n(0)
pci_gnt_n(1)
pci_gnt_n(2)
pci_gnt_n(3)
pci_gnt_n(4)
pci_gnt_n(5)
Figure 9: PCI_Arbiter Grant to a Second Master After First Fails to Respond
X495_09_101306
Figure 10 shows the situation of a master agent, number one, requesting access, as another agent,
number two also requests access. After agent number one fails to respond and deasserts request, the
PCI_Arbiter grants access to the second requesting agent, number two. Agent number two then
becomes the last active master and the park master
DS495 April 8, 2009
www.xilinx.com
9
Product Specification