Achronix Speedster22i 10G/40G/100G Ethernet - Manual (Page 42)

42 UG029, September 6, 2013
sys_clk
ff_rx_data[511:0]
ff_rx_sop[0]
ff_rx_eop[0]
ff_rx_mod[5:0]
ff_rx_err[0]
ff_rx_vlan[1:0]
ff_rx_err_stat[23:0]
ff_rx_dval[0]
ff_rx_rdy[0]
ff_rx_preamble_val
ff_rx_preamble[55:0]
Figure 18: FIFO Receive Interface – Frame Transfer with User Pause
Frame Status
When frame reception terminates, the MAC Core writes a status word in a dedicated internal
FIFO to report information and events to the user application per frame. The status is
available with each frame with the last word of the frame (ff_rx_eop asserted) and is
presented on the ff_rx_err_stat[23:0] data bus.

Invalid length (frame too long/short)

CRC-32 error

Link error (code violation)

FIFO overflow exception

Sequence error (e.g. local or remote fault)

Frame error character

VLAN/Stacked VLAN frame indication

Frame length/type field. This is a copy of the length/type field as it is found in the
frame. Note that for VLAN frames, the value immediately following the 4-octet
VLAN tag is copied here.
If any of the error conditions happened, in addition the ff_rx_err signal will be asserted
together with the frame's last word. Note that the receive status signals
ff_rx_err_stat[23:0] can only be mapped to any segment of FIFO group 0 (10G: SEG0-
3, 40G: SEG0, 100G: SEG0). The per segment status signals ff_rx_err and
ff_rx_vlan[1:0] provide information about error conditions as well as VLAN/Stacked
VLAN frame indications to the user application on a per segment basis.
The frame status word is defined in the table below.