diff --git a/firmware/src_simtrace/card_emu.c b/firmware/src_simtrace/card_emu.c
index 55d227ff..cf3f87b5 100644
--- a/firmware/src_simtrace/card_emu.c
+++ b/firmware/src_simtrace/card_emu.c
@@ -772,27 +772,38 @@ void card_emu_io_statechg(struct card_handle *ch, enum card_io io, int active)
 {
 	switch (io) {
 	case CARD_IO_VCC:
-		if (active == 0) {
+		if (active == 0 && ch->vcc_active == 1) {
+			TRACE_DEBUG("VCC deactivated\n\r");
 			tc_etu_disable(ch->tc_chan);
 			card_set_state(ch, ISO_S_WAIT_POWER);
-		} else if (active == 1 && ch->vcc_active == 0)
+		} else if (active == 1 && ch->vcc_active == 0) {
+			TRACE_DEBUG("VCC activated\n\r");
 			card_set_state(ch, ISO_S_WAIT_CLK);
+		}
 		ch->vcc_active = active;
 		break;
 	case CARD_IO_CLK:
-		if (active == 1 && ch->state == ISO_S_WAIT_CLK)
-			card_set_state(ch, ISO_S_WAIT_RST);
+		if (active == 1 && ch->clocked == 0) {
+			TRACE_DEBUG("CLK activated\n\r");
+			if (ch->state == ISO_S_WAIT_CLK)
+				card_set_state(ch, ISO_S_WAIT_RST);
+		} else if (active == 0 && ch->clocked == 1) {
+			TRACE_DEBUG("CLK deactivated\n\r");
+		}
 		ch->clocked = active;
 		break;
 	case CARD_IO_RST:
-		if (active == 0 && ch->in_reset &&
-		    ch->vcc_active && ch->clocked) {
-			/* enable the TC/ETU counter once reset has been released */
-			tc_etu_enable(ch->tc_chan);
-			card_set_state(ch, ISO_S_WAIT_ATR);
-			/* FIXME: wait 400 to 40k clock cycles before sending ATR */
-			card_set_state(ch, ISO_S_IN_ATR);
-		} else if (active) {
+		if (active == 0 && ch->in_reset) {
+			TRACE_DEBUG("RST released\n\r");
+			if (ch->vcc_active && ch->clocked) {
+				/* enable the TC/ETU counter once reset has been released */
+				tc_etu_enable(ch->tc_chan);
+				card_set_state(ch, ISO_S_WAIT_ATR);
+				/* FIXME: wait 400 to 40k clock cycles before sending ATR */
+				card_set_state(ch, ISO_S_IN_ATR);
+			}
+		} else if (active && !ch->in_reset) {
+			TRACE_DEBUG("RST asserted\n\r");
 			tc_etu_disable(ch->tc_chan);
 		}
 		ch->in_reset = active;