diff --git a/df_datalink_sp/src/system_monitor.c b/df_datalink_sp/src/system_monitor.c
index 7399e56..41f1271 100644
--- a/df_datalink_sp/src/system_monitor.c
+++ b/df_datalink_sp/src/system_monitor.c
@@ -56,7 +56,7 @@ inline uint8_t GetWritable(PINGPONG ctrllor)
 inline uint8_t GetReadable(PINGPONG ctrllor)
 {
 	if (ctrllor.wBusy == BUFF_NONE || ctrllor.wBusy != ctrllor.latest)
-		return ctrllor.latest;
+		return ((ctrllor.latest == BUFF_NONE) ? BUFF_A : BUFF_B);
 	else
 		return ((ctrllor.wBusy == BUFF_B) ? BUFF_A : BUFF_B);
 }