summaryrefslogtreecommitdiff
path: root/digital/asserv/src/hdlcounter/updown_counter.v
diff options
context:
space:
mode:
Diffstat (limited to 'digital/asserv/src/hdlcounter/updown_counter.v')
-rw-r--r--digital/asserv/src/hdlcounter/updown_counter.v55
1 files changed, 55 insertions, 0 deletions
diff --git a/digital/asserv/src/hdlcounter/updown_counter.v b/digital/asserv/src/hdlcounter/updown_counter.v
new file mode 100644
index 00000000..04f73bbd
--- /dev/null
+++ b/digital/asserv/src/hdlcounter/updown_counter.v
@@ -0,0 +1,55 @@
+// updown_counter.v - Up and down counter.
+// hdlcounter - Incremental encoder counter on programmable logic. {{{
+//
+// Copyright (C) 2007 Nicolas Schodet
+//
+// Robot APB Team 2008.
+// Web: http://apbteam.org/
+// Email: team AT apbteam DOT org
+//
+// 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 2 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, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+//
+// }}}
+`timescale 1ns / 1ps
+
+module updown_counter(clk, rst, updown, counter);
+ parameter bits = 8;
+ input clk;
+ input rst;
+ // Bit updown[1] is for up and bit updown[0] is for down.
+ input [1:0] updown;
+ output [bits-1:0] counter;
+
+ reg [bits-1:0] counter;
+
+ always @(posedge clk or negedge rst) begin
+ if (!rst) begin
+ counter <= 0;
+ end
+ else begin
+ case (updown)
+ 2'b00:
+ counter <= counter;
+ 2'b10:
+ counter <= counter + 1;
+ 2'b01:
+ counter <= counter - 1;
+ // Do not synthesis useless logic, 2'b11 is an undefined case.
+ default:
+ counter <= { bits { 1'bX }};
+ endcase
+ end
+ end
+endmodule