When not electing to provide the Command Field In-line with the frame sent for transmission, it must instead be provided out-of-band. This is achieved by expanding the size of the signal from that already defined in the current AXI4-Stream Interface – Transmit (see the Tri-Mode Ethernet MAC LogiCORE IP Product Guide (PG051).
Selecting this mode is through an AXI4-Lite addressable configuration bit (see the following table).
The signal definition for this expanded
tx_axis_tuser
is defined in the following table. A
timing diagram showing the operation of this signal for normal frame transmission
follows the following table. To summarize, the Command Field bits of tx_axis_tuser
must be valid on the same clock cycle when the
first data word of the frame is sent for transmission.
Bits | Name | Description |
---|---|---|
tx_axis_tuser [0] | Underrun | AXI4-Stream user signal used to signal explicit underrun. This is defined in the 1G/2.5G Ethernet PCS/PMA or SGMII LogiCORE IP Product Guide (PG047) and Tri-Mode Ethernet MAC LogiCORE IP Product Guide (PG051). |
tx_axis_tuser[63:1] | Reserved | Reserved for future use (all bits are ignored). |
tx_axis_tuser[127:64] | Command Field |
A 64-bit field as per the Command Field definition of Table 1. This field is only valid when you have elected not to use the In-Line option of Providing the Command Field In-Line. (Otherwise, all of these bits are ignored). |