1//
2// Copyright 2011 Ettus Research LLC
3//
4// This program is free software: you can redistribute it and/or modify
5// it under the terms of the GNU General Public License as published by
6// the Free Software Foundation, either version 3 of the License, or
7// (at your option) any later version.
8//
9// This program is distributed in the hope that it will be useful,
10// but WITHOUT ANY WARRANTY; without even the implied warranty of
11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12// GNU General Public License for more details.
13//
14// You should have received a copy of the GNU General Public License
15// along with this program.  If not, see <http://www.gnu.org/licenses/>.
16//
17
18
19module ll8_to_txmac
20  (input clk, input reset, input clear,
21   input [7:0] ll_data, input ll_sof, input ll_eof, input ll_src_rdy, output ll_dst_rdy,
22   output [7:0] tx_data, output tx_valid, output tx_error, input tx_ack );
23
24   reg [2:0] xfer_state;
25
26   localparam XFER_IDLE      = 0;
27   localparam XFER_ACTIVE    = 1;
28   localparam XFER_WAIT1     = 2;
29   localparam XFER_UNDERRUN  = 3;
30   localparam XFER_DROP      = 4;
31
32   always @(posedge clk)
33     if(reset | clear)
34       xfer_state 	    <= XFER_IDLE;
35     else
36       case(xfer_state)
37	 XFER_IDLE :
38	   if(tx_ack)
39	     xfer_state <= XFER_ACTIVE;
40	 XFER_ACTIVE :
41	   if(~ll_src_rdy)
42	     xfer_state <= XFER_UNDERRUN;
43	   else if(ll_eof)
44	     xfer_state <= XFER_WAIT1;
45	 XFER_WAIT1 :
46	   xfer_state <= XFER_IDLE;
47	 XFER_UNDERRUN :
48	   xfer_state <= XFER_DROP;
49	 XFER_DROP :
50	   if(ll_eof)
51	     xfer_state <= XFER_IDLE;
52       endcase // case (xfer_state)
53
54   assign ll_dst_rdy 	 = (xfer_state == XFER_ACTIVE) | tx_ack | (xfer_state == XFER_DROP);
55   assign tx_valid 	 = (ll_src_rdy & (xfer_state == XFER_IDLE))|(xfer_state == XFER_ACTIVE);
56   assign tx_data 	 = ll_data;
57   assign tx_error 	 = (xfer_state == XFER_UNDERRUN);
58
59endmodule // ll8_to_txmac
60
61