From 36d298a2b67a71220c91338ff3736ef680cdc1a3 Mon Sep 17 00:00:00 2001
From: Cary R <cygcary@yahoo.com>
Date: Fri, 11 Nov 2011 17:52:01 -0800
Subject: [PATCH] Assert that sync/async set/clear are not supported for a DFF
 primitive.

Since synthesis is not currently supported we do not support/generate
sync/async set or clear control inputs. This is further complicated by
the fact that the VVP DFF primitive is not fully implemented.
---
 tgt-vvp/vvp_scope.c | 48 ++++++++++++++++++++-------------------------
 1 file changed, 21 insertions(+), 27 deletions(-)

diff --git a/tgt-vvp/vvp_scope.c b/tgt-vvp/vvp_scope.c
index ec35db024..24b0e98dc 100644
--- a/tgt-vvp/vvp_scope.c
+++ b/tgt-vvp/vvp_scope.c
@@ -1622,51 +1622,45 @@ static void draw_lpm_concat(ivl_lpm_t net)
 }
 
 /*
- *  primitive FD (q, clk, ce, d);
- *    output q;
- *    reg q;
- *    input clk, ce, d;
- *    table
- *    // clk ce  d r s   q   q+
- *        r   1  0 0 0 : ? : 0;
- *        r   1  1 0 0 : ? : 1;
- *        f   1  ? 0 0 : ? : -;
- *        ?   1  ? 0 0 : ? : -;
- *        *   0  ? 0 0 : ? : -;
- *        ?   ?  ? 1 ? : ? : 0;
- *        ?   ?  ? 0 1 : ? : 1;
- *    endtable
- *  endprimitive
+ * Emit a DFF primitive. This uses the following syntax:
+ *
+ * .dff <data>, <clock>, <enable>, <async>;
+ *
+ * The async pin currently sets the stored data value and propagates it
+ * to the output (not very useful). This routine always sets the async
+ * value to high-Z which is ignored in the VVP code. This is all OK
+ * since synthesis is not currently functional.
  */
 static void draw_lpm_ff(ivl_lpm_t net)
 {
-      ivl_expr_t aset_expr = 0;
-      const char*aset_bits = 0;
-
       ivl_nexus_t nex;
-      unsigned width;
-
-      width = ivl_lpm_width(net);
-
-      aset_expr = ivl_lpm_aset_value(net);
-      if (aset_expr) {
-	    assert(ivl_expr_width(aset_expr) == width);
-	    aset_bits = ivl_expr_bits(aset_expr);
-      }
 
+	/* Sync/Async set/clear control is currently only supported in V0.8
+	 * which has working synthesis. If/when this is added see that code
+	 * for clues about how this should be implemented. The dff primitive
+	 * used here (from vvp) needs to be improved to support both an
+	 * async set and clear. See the UDP generated by the tgt-vlog95 code
+	 * generator in V0.10 and later for how this might be done. */
+      assert(ivl_lpm_sync_clr(net) == 0);
+      assert(ivl_lpm_sync_set(net) == 0);
+      assert(ivl_lpm_async_clr(net) == 0);
+      assert(ivl_lpm_async_set(net) == 0);
 
       fprintf(vvp_out, "L_%p .dff ", net);
 
       nex = ivl_lpm_data(net,0);
       assert(nex);
       fprintf(vvp_out, "%s", draw_net_input(nex));
+      assert(width_of_nexus(nex) == ivl_lpm_width(net));;
 
       nex = ivl_lpm_clk(net);
       assert(nex);
+      assert(width_of_nexus(nex) == 1);;
       fprintf(vvp_out, ", %s", draw_net_input(nex));
 
       nex = ivl_lpm_enable(net);
       if (nex) {
+	    assert(width_of_nexus(nex) == 1);;
 	    fprintf(vvp_out, ", %s", draw_net_input(nex));
       } else {
 	    fprintf(vvp_out, ", C4<1>");