diff options
Diffstat (limited to 'eth/rtl/verilog/flow_ctrl_rx.v')
| -rw-r--r-- | eth/rtl/verilog/flow_ctrl_rx.v | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/eth/rtl/verilog/flow_ctrl_rx.v b/eth/rtl/verilog/flow_ctrl_rx.v new file mode 100644 index 000000000..7ded9e08b --- /dev/null +++ b/eth/rtl/verilog/flow_ctrl_rx.v @@ -0,0 +1,85 @@ +
+// RX side of flow control -- when we are running out of RX space, send a PAUSE
+
+module flow_ctrl_rx
+ (input rst,
+ //host processor
+ input pause_frame_send_en,
+ input [15:0] pause_quanta_set,
+ input [15:0] fc_hwmark,
+ input [15:0] fc_lwmark,
+ // From MAC_rx_ctrl
+ input rx_clk,
+ input [15:0] rx_fifo_space,
+ // MAC_tx_ctrl
+ input tx_clk,
+ output reg xoff_gen,
+ output reg xon_gen,
+ input xoff_gen_complete,
+ input xon_gen_complete
+ );
+
+ // ******************************************************************************
+ // Force our TX to send a PAUSE frame because our RX is nearly full
+ // ******************************************************************************
+
+ reg xon_int, xoff_int;
+ reg [21:0] countdown;
+
+ always @(posedge rx_clk or posedge rst)
+ if(rst)
+ begin
+ xon_int <= 0;
+ xoff_int <= 0;
+ end
+ else
+ begin
+ xon_int <= 0;
+ xoff_int <= 0;
+ if(pause_frame_send_en)
+ if(countdown == 0)
+ if(rx_fifo_space < fc_lwmark)
+ xoff_int <= 1;
+ else
+ ;
+ else
+ if(rx_fifo_space > fc_hwmark)
+ xon_int <= 1;
+ end // else: !if(rst)
+
+ reg xoff_int_d1, xon_int_d1;
+
+ always @(posedge rx_clk)
+ xon_int_d1 <= xon_int;
+ always @(posedge rx_clk)
+ xoff_int_d1 <= xoff_int;
+
+ always @ (posedge tx_clk or posedge rst)
+ if (rst)
+ xoff_gen <=0;
+ else if (xoff_gen_complete)
+ xoff_gen <=0;
+ else if (xoff_int | xoff_int_d1)
+ xoff_gen <=1;
+
+ always @ (posedge tx_clk or posedge rst)
+ if (rst)
+ xon_gen <=0;
+ else if (xon_gen_complete)
+ xon_gen <=0;
+ else if (xon_int | xon_int_d1)
+ xon_gen <=1;
+
+ wire [15:0] pq_reduced = pause_quanta_set - 2;
+
+ always @(posedge tx_clk or posedge rst)
+ if(rst)
+ countdown <= 0;
+ else if(xoff_gen)
+ countdown <= {pq_reduced,6'd0};
+ else if(xon_gen)
+ countdown <= 0;
+ else if(countdown != 0)
+ countdown <= countdown - 1;
+
+endmodule // flow_ctrl
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