IDT PCI Express 89HPES32NT24xG2, User Manual, Page: 85 / 744

IDT Switch Core
PES32NT24xG2 User Manual 4 - 7 January 30, 2013
Notes
Figure 4.2 Architectural Model of Arbitration
Port arbitration resolves contention when multiple ingress ports target the same egress port. As shown
in Figure 4.2, port arbitration is done independently by each port on the egress side (i.e., port arbitration
regulates TLP entry into the corresponding EFB). Ports are numbered 0 to 23, plus two DMA modules
named DMA module 0 and DMA module 1.
– DMA module 0 is logically associated with function 2 of port 0.
– DMA module 1 is logically associated with function 2 of port 8.
Each port has a dedicated port arbiter. The DMA modules also have a dedicated port arbiter that
controls access into the DMA’s EFB
1
. Ingress ports, or the DMA modules, that wish to transfer one or more
packets to the egress port participate in port arbitration. Prior to participating in port arbitration, each ingress
port does packet ordering. Based on this, each ingress port selects zero, one, or multiple packets as candi-
dates for transfer towards the egress buffers (EFBs).
Each port arbiter performs arbitration according to the configuration of the VC Capability Structure in
function 0 of the corresponding port. Depending on the operating mode of the port (e.g., upstream switch
port, NT function port, upstream switch port with DMA function, etc.), function 0 of the port may be a PCI-to-
PCI bridge function or an NT function.
– If function 0 of the port is a PCI-to-PCI bridge function, then the VC Capability Structure associated
with the NT function is ignored and must not be configured by software (i.e., it must not be linked
into the NT function’s capabilities list).
– If function 0 of the port is an NT function, then the VC Capability structure associated with the PCI-
to-PCI bridge function is ignored and must not be configured by software (i.e., it must not be linked
into the PCI-to-PCI bridge function’s capabilities list via the global address space).
1.
The DMA EFB contains packets to be processed by the DMA engine. For more information, contact IDT at
ssdhelp@idt.com.
Port Arbiter
Port 0 Arbitration
Function 0
VC Capability
Structure
Port 0 EFB
VC 0
Request (
Route-to-S
elf)
Request
R
eq
ue
st
R
eq
ue
st
R
eq
ue
st
Port 1 IFB
VC 0
Port 0 IFB
VC 0
Port 23 IFB
VC 0
DMA 0 IFB
VC 0
DMA 1 IFB
VC 0
Port Arbiter
Port 23 Arbitration
Function 0
VC Capability
Structure
Port 23 EFB
VC 0
Port Arbiter
DMA 0 Arbitration
Port 0, Function 0
VC Capability
Structure
DMA 0 EFB
VC 0
Port Arbiter
DMA 1 Arbitration
Port 8, Function 0
VC Capability
Structure
DMA 1 EFB
VC 0