Data Sheet

Ethernet Controller I210 —Interconnects
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The PCIe function interfaces with the PCIe unit through one or more clients. A client ID identifies the
client and is included in the Tag field of the PCIe packet header. Completions always carry the tag value
included in the request to enable routing of the completion to the appropriate client.
Tag IDs are allocated differently for read and write. Messages are sent with a tag of 0x0.
3.1.3.1.1 TAG ID Allocation for Read Transactions
Table 3-1 lists the Tag ID allocation for read accesses. The tag ID is interpreted by hardware in order to
forward the read data to the required device.
3.1.3.1.2 TAG ID Allocation for Write Transactions
Request tag allocation depends on these system parameters:
• DCA supported/not supported in the system (DCA_CTRL.DCA_DIS - refer to Section 8.13.4 for
details)
• TPH enabled in the system.
• DCA enabled/disabled for each type of traffic (TXCTL.TX Descriptor DCA EN, RXCTL.RX Descriptor
DCA EN, RXCTL.RX Header DCA EN, RXCTL.Rx Payload DCA EN).
• TPH enabled or disabled for the specific type of traffic carried by the TLP (TXCTL.TX Descriptor TPH
EN, RXCTL.RX Descriptor TPH EN, RXCTL.RX Header TPH EN, RXCTL.Rx Payload TPH EN).
• System type: Legacy DCA vs. DCA 1.0 (DCA_CTRL.DCA_MODE - refer to Section 8.13.4 for
details).
•CPU ID (RXCTL.CPUID or TXCTL.CPUID).
See the case studies below for information on different implementations
3.1.3.1.2.1 Case 1 - DCA Disabled in the System
Table 3-2 lists the write requests tags. Unlike read, the values are for debug only, allowing tracing of
requests through the system.
Table 3-1. IDs in Read Transactions
Tag ID Description Comment
0x0 Data request 0
0x1 Data request 1
0x2 Data request 2
0x3 Data request 3
0x4 Data request 4
0x5 Data request 5
0x6-017 Not used
0x18 Descriptor Tx
0x19-0x1B Not used
0x1C Descriptor Rx
0x1D-0x1F Not used