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Declare assembler variable for C source file
von Juergen B. (jbaben)

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Hello,

I would like to use an existing function with assembly code in a C 
program.
By this I mean that I want to insert and use an existing function from 
an old program with assembly code into my new C program (C source file, 
assembly code inside a C source file).
How should register R1 (or a general variable) be declared in my 
assembler code in order to be able to use R1 in the C source file?
My function (Assembler-Code)
1
NAME  KEY_BOARD

2
3
TASTEN_PORT     EQU P1             ; benuetzter PORT

4
P_ANZ           EQU  03H           ; Anzahl Portleitungen

5
;TASTATUR_MODUS  BIT  [0]          ; Steuerbit fuer Modus (20.0)

6
EINGAENGE       EQU  00010111B     ; Maske fuer Tastaturport:

7
                   ; Tastaturpins = 1

8
                  ; unbenuetzte Portpins:

9
                  ; Eingaenge : 1

10
                  ; Ausgaenge : 0

11
TASTEN_NUMMER   EQU  01H          ; Register 1

12
SPALTEN_ZAEHLER EQU  02H          ;          2

13
ZEILEN_ZAEHLER  EQU  03H          ;          3

14
AUSGABE_MASKE   EQU  04H          ;          4

15
EINLESE_MASKE   EQU  05H          ;          5

16
17
ZAHLEN          EQU    00H

18
FERTIG          EQU    03H

19
LOESCHEN        EQU    05H

20
  

21
REGISTER_1    EQU  R1

22
;REGISTER_2    EQU  R2

23
  

24
CARRY_BIT    BIT PSW.7  ;CY

25
  

26
;public Register

27
  

28
;?DT?DATA_SEG  segment data

29
;  RSEG  ?DT?DATA_SEG

30
    

31
;Register  ds   1

32
33
?PR?key_board?KEY_BOARD    SEGMENT CODE

34
  EXTRN  CODE (c_func)

35
  EXTRN   CODE (key_input)

36
  EXTRN   DATA (key_in)

37
  PUBLIC  CARRY_BIT

38
  PUBLIC  key_board

39
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  RSEG  ?PR?key_board?KEY_BOARD

41
key_board:

42
;****************************************************************

43
   MOV   A,TASTEN_PORT      ; Pruefen, ob Taste noch

44
   ANL   A,R5               ; aktiv ist

45
   JZ    TADA               ; Sprung, falls Taste aktiv

46
   SJMP  WARTE              ; Modus 0+1 : Taste wieder inaktiv

47
48
TADA:

49
   SJMP  KEINE_TASTE1       ; Modus = 1 : alte Taste noch aktiv

50
51
WARTE:

52
   LCALL ENTPRELL           ; Entprellzeit abwarten

53
   MOV   A,TASTEN_PORT      ; Pruefen ob Taste noch aktiv ist

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   ANL   A,R5

55
   JZ    WARTE              ; Sprung, falls Taste noch prellt

56
57
STARTE_ZYKLUS:

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    MOV   R4,#0FEH           ; Startwert fuer Ausgabemaske

59
    MOV   R1,#00H           ; Startwert fuer Tastennummer

60
    MOV   R2,#P_ANZ         ; Startwert fuer Spaltenzaehler

61
62
....

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   RET

64
65
   END


My C-Programm

1
extern void key_board(void);

2
extern unsigned char R1;     // ?

3
4
main {

5
....

6
 if (R1 == 0x03) { ….. } 

7
....

8
}


I use the Compiler "Keil-C"

Kind Regards
Juergen B.

  


  




  

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