Identifying Pause Packets - 2.1 English

Versal ACAP 600G Channelized Multirate Ethernet Subsystem (DCMAC) LogiCORE IP Product Guide (PG369)

Document ID
PG369
Release Date
2023-04-12
Version
2.1 English

The following process determines if a given frame is a Pause Frame:

  1. Checks are performed to see if a packet is a global or a priority control packet. Packets that pass step 1 are forwarded only if c{0..5}_ctl_rx_forward_control field of the C{0..5}_CONFIGURATION_RX_FLOW_CONTROL_REG1 is set to 1.
  2. If step 1 passes, the packet is checked to determine if it is a global pause packet.
  3. If step 2 fails, the packet is checked to determine if it is a priority pause packet.

In the following pseudo code, DA is the destination address, SA is the source address, OPCODE is the opcode, and ETYPE is the ethertype/length field that are extracted from the incoming packet.

For step 1, the pseudo code for the checking function is:


assign da_match_gcp = (!ctl_rx_check_mcast_gcp && !ctl_rx_check_ucast_gcp) ||
((DA == ctl_rx_pause_da_ucast) && ctl_rx_check_ucast_gcp) ||
((DA == 48'h0180c2000001) && ctl_rx_check_mcast_gcp);

assign sa_match_gcp = !ctl_rx_check_sa_gcp || (SA == ctl_rx_pause_sa);

assign etype_match_gcp = !ctl_rx_check_etype_gcp || (ETYPE == ctl_rx_etype_gcp);

assign opcode_match_gcp = !ctl_rx_check_opcode_gcp ||
((OPCODE >= ctl_rx_opcode_min_gcp) && (OPCODE <= ctl_rx_opcode_max_gcp));

assign global_control_packet = da_match_gcp && sa_match_gcp &&
etype_match_gcp && opcode_match_gcp && ctl_rx_enable_gcp;

assign da_match_pcp = (!ctl_rx_check_mcast_pcp && !ctl_rx_check_ucast_pcp) ||
((DA == ctl_rx_pause_da_ucast) && ctl_rx_check_ucast_pcp) ||
((DA == ctl_rx_pause_da_mcast) && ctl_rx_check_mcast_pcp);

assign sa_match_pcp = !ctl_rx_check_sa_pcp || (SA == ctl_rx_pause_sa);

assign etype_match_pcp = !ctl_rx_check_etype_pcp || (ETYPE == ctl_rx_etype_pcp);

assign opcode_match_pcp = !ctl_rx_check_opcode_pcp ||
((OPCODE >= ctl_rx_opcode_min_pcp) && (OPCODE <= ctl_rx_opcode_max_pcp));

assign priority_control_packet = da_match_pcp && sa_match_pcp &&
etype_match_pcp && opcode_match_pcp && ctl_rx_enable_pcp;

assign control_packet = global_control_packet || priority_control_packet;
For step 2, the following pseudo code shows the checking function:

assign da_match_gpp = (!ctl_rx_check_mcast_gpp && !ctl_rx_check_ucast_gpp) ||
((DA == ctl_rx_pause_da_ucast) && ctl_rx_check_ucast_gpp) ||
((DA == 48'h0180c2000001) && ctl_rx_check_mcast_gpp);


assign sa_match_gpp = !ctl_rx_check_sa_gpp || (SA == ctl_rx_pause_sa);


assign etype_match_gpp = !ctl_rx_check_etype_gpp || (ETYPE == ctl_rx_etype_gpp);


assign opcode_match_gpp = !ctl_rx_check_opcode_gpp || (OPCODE == ctl_rx_opcode_gpp);


assign global_pause_packet = da_match_gpp && sa_match_gpp && etype_match_gpp &&
opcode_match_gpp && ctl_rx_enable_gpp;

For step 3, the following pseudo code shows the checking function:
assign da_match_ppp = (!ctl_rx_check_mcast_ppp && !ctl_rx_check_ucast_ppp) ||
((DA == ctl_rx_pause_da_ucast) && ctl_rx_check_ucast_ppp) ||
((DA == ctl_rx_pause_da_mcast) && ctl_rx_check_mcast_ppp);

assign sa_match_ppp = !ctl_rx_check_sa_ppp || (SA == ctl_rx_pause_sa);

assign etype_match_ppp = !ctl_rx_check_etype_ppp || (ETYPE == ctl_rx_etype_ppp);

assign opcode_match_ppp = !ctl_rx_check_opcode_ppp || (OPCODE == ctl_rx_opcode_ppp);

assign priority_pause_packet = da_match_ppp && sa_match_ppp && etype_match_ppp &&
opcode_match_ppp && ctl_rx_enable_ppp;