1 files changed, 56 insertions, 0 deletions
diff --git a/fpga/usrp2/simple_gemac/flow_ctrl_tx.v b/fpga/usrp2/simple_gemac/flow_ctrl_tx.v
new file mode 100644
index 000000000..620c1ee7b
--- /dev/null
+++ b/fpga/usrp2/simple_gemac/flow_ctrl_tx.v
@@ -0,0 +1,56 @@
+//
+// 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