Hello,
how to declare the register R1 in my assembly code to R1 in the C source file to be able to use:
C-Program
extern void key_board(void); extern unsigned char R1; // ? main { .... if (R1 == 0x03) { ….. } .... }
Assembler-Code
NAME KEY_BOARD TASTEN_PORT EQU P1 ; benuetzter PORT P_ANZ EQU 03H ; Anzahl Portleitungen ;TASTATUR_MODUS BIT [0] ; Steuerbit fuer Modus (20.0) EINGAENGE EQU 00010111B ; Maske fuer Tastaturport: ; Tastaturpins = 1 ; unbenuetzte Portpins: ; Eingaenge : 1 ; Ausgaenge : 0 TASTEN_NUMMER EQU 01H ; Register 1 SPALTEN_ZAEHLER EQU 02H ; 2 ZEILEN_ZAEHLER EQU 03H ; 3 AUSGABE_MASKE EQU 04H ; 4 EINLESE_MASKE EQU 05H ; 5 ZAHLEN EQU 00H FERTIG EQU 03H LOESCHEN EQU 05H ?PR?key_board?KEY_BOARD SEGMENT CODE EXTRN CODE (c_func) EXTRN CODE (key_input) PUBLIC key_board RSEG ?PR?key_board?KEY_BOARD key_board: ;**************************************************************** TASTATUR: MOV A,TASTEN_PORT ; Pruefen, ob Taste noch ANL A,R5 ; aktiv ist JZ TADA ; Sprung, falls Taste aktiv SJMP WARTE ; Modus 0+1 : Taste wieder inaktiv TADA: SJMP KEINE_TASTE1 ; Modus = 1 : alte Taste noch aktiv WARTE: LCALL ENTPRELL ; Entprellzeit abwarten MOV A,TASTEN_PORT ; Pruefen ob Taste noch aktiv ist ANL A,R5 JZ WARTE ; Sprung, falls Taste noch prellt STARTE_ZYKLUS: MOV R4,#0FEH ; Startwert fuer Ausgabemaske MOV R1,#00H ; Startwert fuer Tastennummer MOV R2,#P_ANZ ; Startwert fuer Spaltenzaehler ...... RET END
Kind Regards
Juergen B.
The Arm Compiler (and likely all Arm-based compilers) obey the Arm Procedure Call Standard.
https://github.com/ARM-software/abi-aa/releases
When a function is called, registers r0-r3 are used to pass parameters, and the return value is passed back in r0.
When writing asm code to work with C code, you MUST also obey this same standard.
You may wish to also see this Learning Path:
https://learn.arm.com/learning-paths/microcontrollers/efficient_embedded/
Apologies - I believe from other threads you are using 8051 class devices.
thanks for your advice.
I understood the thing with the assembler function in my C source file.
I will of course convert the assembler function to “C”.
But this is not just a simple function to query keys.
My function:
6 buttons should be queried via three port pins (with three diodes for decoupling).
Juergen