keep old value of trst in case trst isn't modified by mask/val

git-svn-id: https://urjtag.svn.sourceforge.net/svnroot/urjtag/trunk@1470 b68d4a1b-bc3d-0410-92ed-d4ac073336b7

jtag/ChangeLog

@@ -1,5 +1,8 @@
 2009-03-28  Arnim Laeuger  <arniml>
 
+  * src/tap/chain.c (chain_set_pod_signal) : keep old value of trst in
+    case trst isn't modified by mask/val
+
   * src/tap/chain.c: [ 2610857 ] chain_set_pod_signal() looks funky
 
   * UrJTAG.txt: typo

jtag/src/tap/chain.c

@@ -122,7 +122,7 @@ chain_set_pod_signal( chain_t *chain, int mask, int val )
 {
 	int old_val = cable_set_signal( chain->cable, mask, val );
 	int old_trst = (old_val & CS_TRST) ? 1 : 0;
-	int new_trst = (val & mask & CS_TRST)  ? 1 : 0;
+	int new_trst = (((old_val & ~mask) | (val & mask)) & CS_TRST) ? 1 : 0;
 	tap_state_set_trst( chain, old_trst, new_trst );
 	return old_val;
 }