diff --git a/avr/timer.asm b/avr/timer.asm
index 9e080cf..44a7341 100644
--- a/avr/timer.asm
+++ b/avr/timer.asm
@@ -3,8 +3,10 @@
 ; ***************************************************************************
 ; defs
 
-.equ TIMER_FLAGS_100MS = 1
-.equ TIMER_FLAGS_1S    = 2
+.equ TIMER_FLAGS_100MS       = 1
+.equ TIMER_FLAGS_1S          = 2
+
+.equ TIMER_STATE_SYSSTART    = 8 ; onSysStart was already called
 
 
 
@@ -17,6 +19,7 @@
 timerModuleData:
 timerModuleTickCounter:      .byte 1 ; only low byte used
 timerModuleFlags:            .byte 1
+timerModuleState:            .byte 1
 timerModuleCounter10s:       .byte 1
 timerModuleCounter1m:        .byte 1
 timerModuleCounterSecs:      .byte 4
@@ -97,10 +100,25 @@ Timer_Fini:
 Timer_Run:
   in r15, SREG
   cli
-  clr r16
+
+  lds r18, timerModuleState
+  mov r16, r18                       ; r18: state
+  ori r16, TIMER_STATE_SYSSTART
+  sts timerModuleState, r16
+
   lds r17, timerModuleFlags
+  clr r16
   sts timerModuleFlags, r16
   out SREG, r15  ; restore global IRQ flag
+  
+  ; call onSystemStart when first run
+  mov r16, r18                        
+  andi r16, TIMER_STATE_SYSSTART
+  brne Timer_Run_check100
+  push r17
+    rcall onSystemStart
+  pop r17
+Timer_Run_check100:
   mov r16, r17
   andi r16, TIMER_FLAGS_100MS
   breq Timer_Run_l1