Page 307 - Introduction to Microcontrollers Architecture, Programming, and Interfacing of The Motorola 68HC12

284 Chapter 9 Implementation of C Procedures

char *strncpy(char *str_d,char *str_s,int count){char *sd = str d;
0000088A 3B PSHD
0000088B 3B PSHD
0000088C EC88 LDD 8,SP
QQOGQ88E 6C82 STD 2,SP
51 whi le (count—) {
00000890 201A BRA *+28 ;abs = 08AC
6: if(*str_s) *str__d++ = *str_s++;
00000892 EE86 LDX 6,SP
00000894 E600 LDAB 0,X
00000896 270E BEQ *+16 ;abs = 08A6
00000898 EE88 LDX 8,SP
0000089A ED86 LDY 6,SP
0000089C E670 LDAB 1,Y+
0000089E 6B30 STAB 1,X+
000008AO 6E88 STX 8,SP
000008A2 6D86 STY 6,SP
000008A4 2006 BRA *+8 ;abs = 08AC
7: else *str_d++ = '\0';
000008A6 EE88 LDX 8,SP
000008A8 6930 CLR 1,X+
000008AA 6E88 STX 8,SP
5: while(count—) {
000008AC EE80 'LDX 0,SP
000008AE 191F LEAY -1,X
000008BO 6D80 STY 0,SP
000008B2 0475DD TBNE X,*-32 ;abs = 0892
9: return (sd);
000008B5 EC82 LDD 2,SP
10: }
000008B7 1B84 LEAS 4,SP
000008B9 3D RTS
13: void main() { strncpy(sl, s2, 5);
000008BD CC080B LDD #2059 ; this is si
000008CO 3B PSHD
000008C1 CE0800 LDX #2048 ; this is s2
000008C4 34 PSHX
000008C5 C605 LDAB #5 ; this is the rightmost argument
000008C7 87 CLRA
000008C8 07CO BSR *-62 ;abs = 088A
000008CA 1B84 LEAS 4,SP
15: }
000008D2 3D RTS

Figure 9.19. The Strncpy Procedure