Hi.

Please spare me, I'm new to assembly language so my codes may look dirty and unoptimized ^_^; (maybe my english language as well >_<;)

Using assembler, I successfully wrote 2 codes to control 8051. One is an alarm clock. Another is a stopwatch.

I implemented both codes SEPERATELY on real hardware and they work fine.

But when I try to merge them into one code, the stopwatch is not functioning.

I implement an alarm clock using timer1 and use timer2 to control the stop watch. Both runs in 16 bit mode. Timer1 is always counting(actually it's Real time clock code from the tutorial in this site but modified by me). But timer0 will start running(SETB TR0) only when the appropiate button is clicked.

The problem here is when I press the button to start the stopwatch, weird result happen. Instead of seeing the stopwatch starting to count up, everything seems like went back to MAIN function and stay there, freezing.
Posting whole 500+ lines of code here may be impossible so I'll bring only neccessary lines.

; Timer0 interrupt routines

; 1 Tick = 0.05 seconds. My stopwatch can count up to 0.1 seconds detailed.
ORG 000Bh
PUSH ACC
PUSH PSW
CLR TR0
MOV TH0,#HIGH RESET_VALUE2
MOV TL0,#LOW RESET_VALUE2
SETB TR0
DJNZ MTICKS,EXIT_RTC2
MOV MTICKS,#2
INC MSEC
MOV R6,MSEC
CJNE R6,#10,EXIT_RTC2
MOV MSEC,#0
INC SECOND
MOV R6,SECOND
CJNE R6,#60,EXIT_RTC2
MOV SECOND,#0
INC MINUTE
MOV R6,MINUTE
CJNE R6,#60,EXIT_RTC2
MOV MINUTE,#0
INC HOUR
EXIT_RTC2:
POP PSW
POP ACC
RETI

; Timer1 interrupt routines
ORG 001Bh
PUSH ACC
PUSH PSW
CLR TR1
MOV TH1,#HIGH RESET_VALUE
MOV TL1,#LOW RESET_VALUE
SETB TR1
DJNZ TICKS,EXIT_RTC
MOV TICKS,#20
INC SECONDS
MOV A,SECONDS
CJNE A,#60,EXIT_RTC
ADD A,TL1
ANL A,#00001111b
MOV password,A
MOV SECONDS,#0
INC MINUTES
MOV A,MINUTES
CJNE A,#60,EXIT_RTC
MOV MINUTES,#0
INC HOURS
EXIT_RTC:
POP PSW
POP ACC
RETI
MAIN:

;****** Initializing variables for stopwatch
MOV RUNNING,#00
MOV TH0,#HIGH RESET_VALUE ;Initialize timer high-byte
MOV TL0,#LOW RESET_VALUE ;Initialize timer low-byte
MOV MTICKS,#02
MOV MSEC,#00
MOV HOUR,#00
MOV MINUTE,#00
MOV SECOND,#00
;****** Initializing variables for alarm clock.
MOV TH1,#HIGH RESET_VALUE
MOV TL1,#LOW RESET_VALUE
MOV ALARM,#01
MOV HOURS,#00
MOV MINUTES,#00
MOV SECONDS,#58 ; initialize clock at 00:58 so I can test alarm in 2 sec after each run.
MOV HOURS2,#00
MOV MINUTES2,#01 ; set alarm clock to 00:01
MOV TICKS,#20
MOV TMOD,#00010001b
SETB TR1
SETB EA
SETB ET0
SETB ET1
; Main loop
trick:
JB P3.0,SKIP01
JMP ADDMIN
SKIP01:
JNB P3.1,ADDHOUR
JNB P3.2,ADDALAMMIN
JNB P3.3,ADDALAMHOUR
JB P2.6,SKIP02 ;Check for the button to start/stop the stopwatch
JMP MODESELECT
SKIP02:
JB P2.7,SKIP03 ; Check if the button for Reseting the stopwatch is pressed.
JMP RESET1
SKIP03:
; These lines is the LCD display functions which display both alarmclock and the stopwatch in the same time.

; *** Problem is here
MODESELECT: ; Choosing which to do between start/pause the stopwatch
MOV A,RUNNING
CJNE A,#01,START01b
jmp STOP01a

START01b:
MOV RUNNING,#01
SETB TR0
jmp trick

STOP01a:
MOV RUNNING,#00
CLR TR0
jmp trick


When I pressed P2.6 button(make it go low). The program should have entered MODESELECT (like it did before I merge 2 codes together). Instead, the LCD display 00:00:58(these values are initialized in MAIN) and freeze here.

How come it went back to MAIN ? I've checked everylines and found no way it can return to MAIN function.

I post this because I'm just curious. There's no need to make this work or anything. And my apology for the very long post >_<;