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//
// Copyright 2011 Ettus Research LLC
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
// TX side of flow control -- when other side sends PAUSE, we wait
module flow_ctrl_tx
(input rst,
input tx_clk,
//host processor
input tx_pause_en,
// From MAC_rx_ctrl
input [15:0] pause_quanta,
input pause_quanta_val,
// MAC_tx_ctrl
output pause_apply,
input paused);
// ******************************************************************************
// Inhibit our TX from transmitting because they sent us a PAUSE frame
// ******************************************************************************
// Pauses are in units of 512 bit times, or 64 bytes/clock cycles, and can be
// as big as 16 bits, so 22 bits are needed for the counter
reg [15+6:0] pause_quanta_counter;
reg pqval_d1, pqval_d2;
always @(posedge tx_clk) pqval_d1 <= pause_quanta_val;
always @(posedge tx_clk) pqval_d2 <= pqval_d1;
always @ (posedge tx_clk or posedge rst)
if (rst)
pause_quanta_counter <= 0;
else if (pqval_d1 & ~pqval_d2)
pause_quanta_counter <= {pause_quanta, 6'b0};
else if((pause_quanta_counter!=0) & paused)
pause_quanta_counter <= pause_quanta_counter - 1;
assign pause_apply = tx_pause_en & (pause_quanta_counter != 0);
endmodule // flow_ctrl
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