--- a/src/cs/layer1/cfile/l1_pwmgr.c	Sat Dec 29 04:06:37 2018 +0000
+++ b/src/cs/layer1/cfile/l1_pwmgr.c	Sun Jan 06 21:12:51 2019 +0000
@@ -782,7 +782,7 @@
     #if (W_A_CALYPSO_PLUS_SPR_19599 == 1)
       BOOL     extended_page_mode_state = 0;       //Store state of extended page mode
     #endif
-    WORD32 time_from_last_wakeup=0;
+    WORD32 time_from_last_wakeup, min_time_from_last_wakeup;
     UWORD32  sleep_mode;
 
     #if (OP_BT == 1)
@@ -793,8 +793,33 @@
     why_big_sleep = BIG_SLEEP_DUE_TO_UNDEFINED;
     wakeup_type   = WAKEUP_FOR_UNDEFINED;
 
+    /*
+     * FreeCalypso change: TI's original code implemented logic to
+     * suppress both big and deep sleep (i.e., retry on the next frame)
+     * if less than 7 frames have elapsed since the last wakeup and
+     * if the previous sleep cycle was CLOCK_STOP.  We are changing
+     * this logic in two ways: the check has been moved up here
+     * (originally the check code was way down, wasting work on other
+     * logic if there will be no sleep anyway), and we additionally
+     * suppress both big and deep sleep (effecting retry on the next
+     * frame) if the previous sleep cycle was FRAME_STOP and less than
+     * 5 frames have elapsed since wakeup.  The reason for the latter
+     * addition is that we now allow big sleep while UART and/or SIM
+     * activity timers are running (suppressing deep sleep), and
+     * holding off for 5 frames before going into another big sleep
+     * keeps us from fluttering in and out of big sleep as the external
+     * host or the SIM is trying to talk to us.
+     */
     time_from_last_wakeup = (sleep_time - last_wakeup + 42432) % 42432;
 
+    if (previous_sleep == CLOCK_STOP)
+      min_time_from_last_wakeup = 7;
+    else
+      min_time_from_last_wakeup = 5;
+
+    if (time_from_last_wakeup < min_time_from_last_wakeup)
+      return;
+
     //=================================================
     // check System (SIM, UART, LDC ..... )
     //=================================================
@@ -844,10 +869,15 @@
     // return and wait end of this activity (few TDMA frames) then check on next TDMA frames
     // if MS can go in deep sleep
     /*
-     * FreeCalypso change: the abstention from big sleep because of UART or SIM
-     * has been moved into Cust_check_system(), which now returns DO_NOT_SLEEP
-     * in these cases, while still returning FRAME_STOP if the cause is
-     * the backlight or charging.
+     * FreeCalypso change: we no longer abstain from big sleep because of UART
+     * and SIM activity timers, i.e., when deep sleep is suppressed because of
+     * either of those, we go into big sleep instead.  We also do big sleep
+     * if deep sleep is disallowed because of the backlight or charging.
+     * However, if the UART issue is not the running activity timer, but some
+     * output being drained from the Tx FIFO, for that case our new code in
+     * Cust_check_system() will return DO_NOT_SLEEP (checked above), causing
+     * us to retry on the next frame and hopefully go into deep sleep after
+     * another frame or two.
      */
     if (    !min_time
          || !HWtimer
@@ -933,6 +963,8 @@
         l1s.pw_mgr.sleep_performed = FRAME_STOP;
 
 
+      /* FreeCalypso change: check moved up and extended */
+    #if 0
       if ((previous_sleep == CLOCK_STOP) && (time_from_last_wakeup < 7))
       {
 		#if (CODE_VERSION != SIMULATION)
@@ -944,6 +976,7 @@
 		#endif // NOT SIMULATION
         return;
       }
+    #endif
 
      // update previous sleep
        previous_sleep = l1s.pw_mgr.sleep_performed;