// 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        pause_quanta_sub);

   // ******************************************************************************        

   // Inhibit our TX from transmitting because they sent us a PAUSE frame

   // ******************************************************************************

   reg [15:0] 	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; 

     else if((pause_quanta_counter!=0) & pause_quanta_sub)

       pause_quanta_counter <= pause_quanta_counter - 1;

   assign	pause_apply = tx_pause_en & (pause_quanta_counter != 0);

endmodule // flow_ctrl