Unsigned double byte divided by single byte (51 single chip microcomputer, assembly source code)

The shift-subtraction algorithm is used. The source code is as follows:

 1 ;//////////////////////////////////////////////// /////////////////////////////////

 2 ; Function: div_u16_u8

 3 ; Description: Unsigned double byte divided by single byte

 4; Entry: (R6,R7)/(R0)

 5; Export: (R6,R7).(R5)

 6 ;Note: The remainder is in R5; when OV=1, it indicates overflow

 7 ; Impact: A,B,R0,R5,R6,R7

 8 div_u16_u8: mov r5,#0

 9 mov b,#16

10 #ifdef __SPEED_P__

11 mov a,r6 ; When the high byte is less than the divisor, just shift 8 times

12 jz _du168_line_03

13 clr c

14 subb a,r0        

15 jnc_du168_loop_00

16         

17 mov b,#8

18 clr a        

19 xch a,r7

20 xch a,r6

21 xch a,r5

22 sjmp _du168_loop_00

twenty three 

24 _du168_line_03: mov a,r7

25 mov b,r0

26 div ab

27 mov r7,a

28 mov r5,b

29 sjmp _du168_line_04

30 #endif

31 _du168_loop_00: clr c

32 

33 mov a,r7 ; shift left

34 rlc a

35 mov r7,a

36         

37 mov a,r6

38 rlc a

39 mov r6,a

40         

41 mov a,r5

42 rlc a

43 mov r5,a

44         

45 mov F0,c ; shift out bit = 1, or when the high byte is enough to subtract, the quotient + 1

46 clr c

47 subb a,r0

48 anl c,/F0

49 jc _du168_line_01

50 mov r5,a

51 inc r7

52 _du168_line_01: djnz b,_du168_loop_00

53 

54 _du168_line_04: mov a,r5 ; round up

55 add a,r5

56 jc _du168_line_02

57 subb a,r0

58 jc return_du168

59 _du168_line_02: clr c

60 mov a,#1

61 add a,r7

62 mov r7,a

63 clr a

64 addc a,r6

65 mov r6,a

66 

67 return_du168: mov OV,C

68 ret