Tim Ahrens

C Question

Discussion created by Tim Ahrens on Jan 19, 2008
Latest reply on Jan 30, 2008 by bigmac
Hi Folks,

Being a noob to C, and only having a little hair left, here's a question.
Simple decision box:
Check to see if location Key_temp is = 0.  If not, wait till it changes (done via I-rupt routine).
When it becomes non-zero, then check Month_current to see if it is 12.  If so,
then make it 01, then go do some housekeeping.
First, I tried with only the 1st comparison to Key_temp, & here's what I got:
C code:                                                                                            Assembly
void do_month(void){                                                                     199A  TST  0xB5
                                                                                                       199C Beq *-2      ;abs = 0x199A
    while (Key_temp == 0);   // wait until there is a key available    199E  NOP
                                                                                                       199F  RTS
    if(Key_temp==0x48);      //Up - short?           
The while instruction worked fine, but what happened to the if(Key....) assembly code?
In my real code, the first decision tree (Key_temp=48), should be followed by a second decision,
if  (Month_current=12).
When I do the following:
void do_month(void){                                                      199A  TST 0xB5
    while (Key_temp == 0);       // wait                              199C  BEQ *-2
                                                                                        199E  LDA 0xBC  (location Month_current)
    if(Key_temp==0x48);          //Up - short?                    
19A0  CMP #0x0C
       if(Month_current==12){                                            19A2  BNE *-8    ;abs = 0x19AA
         Month_current=1;                                                   19A4  MOV #0x01,0xBC
         Update_month();                                                    19A7  JMP 0x19AB
       }                                                                                19AA  RTS
Figured I'd see what I'm doing wrong before I go nuts!!