Index: sys/dev/ow/owc_gpiobus.c
===================================================================
--- sys/dev/ow/owc_gpiobus.c
+++ sys/dev/ow/owc_gpiobus.c
@@ -279,6 +279,8 @@
 	if (error != 0)
 		return (error);
 
+	critical_enter();
+
 	/* Force low for t_lowr microseconds */
 	then = sbinuptime();
 	OUTPIN(sc);
@@ -291,14 +293,13 @@
 	 * master's pushing the line low.
 	 */
 	INPIN(sc);
-	critical_enter();
 	do {
 		now = sbinuptime();
 		GETPIN(sc, &sample);
-	} while (sbttous(now - then) < t->t_rdv + 2 && sample == 0);
+	} while (now - then < (t->t_rdv + 2) * SBT_1US && sample == 0);
 	critical_exit();
 
-	if (sbttons(now - then) < t->t_rdv * 1000)
+	if (now - then < t->t_rdv * SBT_1US)
 		*bit = 1;
 	else
 		*bit = 0;
@@ -306,7 +307,7 @@
 	/* Wait out the rest of t_slot */
 	do {
 		now = sbinuptime();
-	} while ((now - then) / SBT_1US < t->t_slot);
+	} while (now - then < (t->t_slot + 2 * t->t_rec) * SBT_1US);
 
 	RELBUS(sc);