Z80: added simple modelling of charge sharing to deal with so Z80 flo…

…ating node issues

netlist_sim.c

@@ -61,6 +61,7 @@ typedef struct {
 } list_t;
 
 typedef struct {
+	BOOL chargeSharing;
 	nodenum_t nodes;
 	nodenum_t transistors;
 	nodenum_t vss;
@@ -380,6 +381,32 @@ getGroupValue(state_t *state)
 	}
 }
 
+static inline BOOL
+getGroupValueChargeSharing(state_t *state)
+{
+	switch (state->group_contains_value) {
+		case contains_vcc:
+		case contains_pullup:
+			return YES;
+		case contains_vss:
+		case contains_pulldown:
+			return NO;
+		default:
+			break;
+	}
+	BOOL max_state = NO;
+	int max_connections = 0;
+	for (int i = 0; i < group_count(state); i++) {
+		nodenum_t nn = group_get(state, i);
+		int connections = state->nodes_gatecount[nn] + state->nodes_c1c2count[nn];
+		if (connections > max_connections) {
+			max_connections = connections;
+			max_state = get_nodes_value(state, nn);
+		}
+	}
+	return max_state;
+}
+
 static inline void
 recalcNode(state_t *state, nodenum_t node)
 {
@@ -390,7 +417,7 @@ recalcNode(state_t *state, nodenum_t node)
 	addAllNodesToGroup(state, node);
 
 	/* get the state of the group */
-	BOOL newv = getGroupValue(state);
+	BOOL newv = state->chargeSharing ? getGroupValueChargeSharing(state) : getGroupValue(state);
 
 	/*
 	 * - set all nodes to the group state
@@ -457,6 +484,12 @@ recalcNodeList(state_t *state)
  *
  ************************************************************/
 
+void
+modelChargeSharing(state_t *state, BOOL enabled)
+{
+   state->chargeSharing = enabled;
+}
+
 static inline void
 add_nodes_dependant(state_t *state, nodenum_t a, nodenum_t b)
 {
@@ -482,6 +515,7 @@ setupNodesAndTransistors(netlist_transdefs *transdefs, BOOL *node_is_pullup, nod
 {
 	/* allocate state */
 	state_t *state = malloc(sizeof(state_t));
+	state->chargeSharing = NO;
 	state->nodes = nodes;
 	state->transistors = transistors;
 	state->vss = vss;

netlist_sim.h

@@ -10,3 +10,5 @@ void writeNodes(state_t *state, int count, nodenum_t *nodelist, int v);
 
 void recalcNodeList(state_t *state);
 void stabilizeChip(state_t *state);
+
+void modelChargeSharing(state_t *state, BOOL enabled);

perfectz80.c

@@ -417,6 +417,8 @@ initAndResetChip(int argc, char *argv[])
                                  vss,
                                  vcc);
 
+   modelChargeSharing(state, YES);
+
    setNode(state, _reset, 0);
    setNode(state, clk,    1);
    setNode(state, _busrq, 1);