Dear Guys,

I've written a program for the Atmel 8052 chip that would run a stepper motor. However I keep finding that my program freezes-up after may be 100 - 120 cycles ( the program runs in a loop, depending on the task that the motor must perform).

I use some 'sjmp' and 'ljmp' command, thus don't know what could be the problem.

Sample Program :

BaudLoad equ -36 ;9600 at 18.432MHz
Smod equ 0
DIR equ P1.0
CONTROL bit P1.1
ENABLE bit P1.2
;FULL bit P1.3
V5 bit P1.3
I3 bit p1.4
I2 bit P1.5
I1 bit p1.6
I4 bit P1.7

HIGH_CURRENT bit P2.0
EN_245 bit P0.0
RESET bit P0.1
FULL bit P0.2
HOME bit P0.3
CLK bit P0.4
DIR_245 bit P0.5
V36 bit P0.6

org 00h
ljmp start
; org 03h
; ljmp ISR0
; org 013h
; ljmp ISR1

org 30h
start: acall init_ports
acall request_print
sjmp start


mov r3,#0h

;Main Section
;Displays > and waits for 3 types of command namely '.','5','7'. If
Restart:
L1: mov r5,#0h
setb high_current
acall init1
mov a,#'>' ; Command prompt
acall send
command: acall init2
acall receive
cjne a,#'.',not_dot ; Request to Power Down
acall pwr_off
not_dot: cjne a,#05h,not_06
acall Initialize_Motor ; Request to Initialize Motor
not_06: cjne a,#35h,not_05 ; Request to Print
acall Request_Print

not_05: sjmp L1

; mov IE,#81h
; setb it1 ; Level Activate for Interupts

;-----------------------------------------------------------------------------
; Initialize Motor to Ref. sensor location
; Acc = Motor Speed
; I4 = Ref. Position
; I3 = Max. Position
;-----------------------------------------------------------------------------
Initialize_Motor:
acall pwr_on ; Move the board
clr high_current ; High speed switch
clr full ; Req. for Half step mode
clr dir ; set a direction
mov a,#50 ; Move motor speed
mov r1,#0
muharam: mov r2,#13
shawal: mov r3,#200
ramadan: jnb i4,i4_slow
jnb i3,i3_slow
setb clk
acall clock
clr clk
acall clock
djnz r3,ramadan
djnz r2,shawal
djnz r1,muharam
acall init1
mov r6,#02 ; Cannot Initialize
ljmp error_dump

i3_slow: setb dir ; Cpl direction
clr reset
acall mdelay
acall mdelay
setb reset
acall mdelay
acall mdelay
mov r7,#10 ; Move out of sensor slightly
i3_slow1: setb clk
acall clock
clr clk
acall clock
djnz r7,i3_slow1
sjmp ramadan

i4_slow: clr dir
vikna: acall init1
mov a,#06h ; Initialization OK, Motor = Min.
acall send
sjmp L1
;-----------------------------------------------------------------------------
;Request to Print
;
;
;-----------------------------------------------------------------------------
Request_Print:
acall pwr_on ; Move the board
clr full ; Req. for Half step mode
clr dir ; set a direction
jnb I4,min_pos
jnb I3,max_pos
mov r6,#54
acall error_dump ; Cannot Print, Head out of position

min_pos: mov R6,#06h
acall dump_host
mov R6,#2Fh
acall dump_host
clr dir
sjmp cont_hitam

max_pos: mov R6,#06h
acall dump_host
mov R6,#2Bh
acall dump_host
setb dir

cont_hitam: acall init2
acall receive
cjne a,#'.',not_quit
acall pwr_off
not_quit: cjne a,#'t',not_print
print: acall init2
acall receive
clr high_current
mov r7,a
mov r0,#20
Yanty: setb clk
acall clock
clr clk
acall clock
djnz r0,yanty
mov r0,#15
Abdul_Karim: mov r1,#200
Sharril: setb clk
acall clock
clr clk
acall clock
jnb i3,i3_found ; is mAX sensor activated
jnb i4,i4_found
djnz r1,sharril
djnz r0,abdul_karim
mov r6,#'3'
ljmp error_dump

i4_found:
i3_found: mov R6,#06h
acall dump_host
clr reset
acall mdelay
acall mdelay
acall mdelay
setb reset
not_print: ljmp restart

error1: mov r6,#49
sjmp error_dump


error_dump: acall init1
mov a,#15h ; NACK
acall send
dump_error: mov a,R6 ; Error 3
acall send
ljmp pwr_off
sjmp dump_error
dump_host: acall init1
mov a,R6
acall send
ret

init1: mov pcon,#80h
mov scon,#40h ;send mode
clr tr1 ;stop baudrate generator
mov tmod,#20h ;n - 8 - 1
mov tl1,#0fdh ;preload autoreload registers on 4800 bps = 0fah
mov th1,#0fdh ;preload autoreload registers on 4800 bps = 0fah
setb tr1 ;start baudrate generator
ret

INIT2:
mov pcon,#80h
mov scon,#50h ;receive mode
clr tr1 ;idem
mov tmod,#20h
mov tcon,#41h
mov tl1,#0fdh
mov th1,#0fdh
setb tr1 ;idem
ret ;return from isr

INIT_PORTS:
mov p0,#11000000b
mov p1,#11111000b
setb p3.2
setb p3.3
setb control
setb enable
clr full
setb reset
clr dir
; setb high_current
ret

SEND:
trans: mov sbuf,a ;load sbuf with char from acc
loop1: jnb ti,loop1 ;flush char - if ti==1 then char is flushed
clr ti ;reset ti
ret
ajmp truncate ;go to receive routine

truncate: ajmp receive

RECEIVE: acall flushsbuf
loop2: jnb ri,$ ;$-sign means address of current label 'loop'
mov a,sbuf
clr ri ;reset ri-flag
ret

flushsbuf: mov a,sbuf ;preserve sbuf in acc
ret ;return from isr

not_rite: ajmp loop2

ISR0: push psw
push acc
acall init1
mov a,#'F' ; Denote V5_AUX shutdown
acall send
pop acc
pop psw
reti

PWR_ON:
clr V5
acall mdelay
acall mdelay
clr V36
acall mdelay
acall mdelay
setb enable
; mov r2,#100
;shammil:
acall mdelay
acall mdelay
; djnz r2,shammil
jb I1,thermal
ret

Thermal: mov r6,#'1'
ljmp error_dump

PWR_OFF: mov IE,#0h
clr Enable
acall mdelay
setb V36
acall mdelay
setb V5
acall mdelay
setb high_current
ljmp restart

MDELAY: push acc
mov a, #0a6h
md_olp: inc a
nop
nop
nop
nop
nop
nop
nop
nop
jnz md_olp
nop
pop acc
ret


sdelay: push acc
mov a, #91h
sd_olp: inc a
acall mdelay
acall mdelay
acall mdelay
acall mdelay
acall mdelay
acall mdelay
acall mdelay
acall mdelay
acall mdelay
nop
nop
nop
nop
nop
jnz sd_olp
mov a, #33h
sd_ilp: djnz acc, sd_ilp
pop acc
ret

clock: push acc
clock1: dec a
nop
nop
nop
nop
nop
nop
nop
nop
jnz clock1
nop
pop acc
ret

END ;pseudo code for end of assembly file