nehallove
Joined: 16 Jan 2008
Posts: 61
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| is input() function is reentrant ? |
 Posted: Tue Dec 23, 2008 1:12 pm |
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Hi,
I am using pic18f2520 and I am using CCS IDE 4.083. I want to use input() function to read port within an isr routine. But when I am using it first time it reads, but while running again it doesn't read and is stuck in a loop.
Does input() function have the same problem as delay_ms() or not?
thanks
nehal
_________________
nehal |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue Dec 23, 2008 1:30 pm |
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Make a test program. Look at the .LST file. The ASM code will tell you
what is happening.
Notice that the compiler creates a separate instance of the input()
function each time it is called. Also notice that there is no loop in
the code. It can't lock-up.
| Quote: |
.................... #INT_EXT
.................... void ext_isr(void)
.................... {
.................... char c;
....................
.................... c = input(PIN_B0);
009E: BSF F93.0 // Set TRISB.0 = input pin
00A0: CLRF 1A
00A2: BTFSC F81.0 // Read pin B0 and test it.
00A4: INCF 1A,F
....................
.................... }
....................
.................... //=================================
00A6: BCF FF2.1
00A8: GOTO 0058
.................... void main()
.................... {
00AC: CLRF FF8
00AE: BCF FD0.7
00B0: BSF 08.7
00B2: CLRF FEA
00B4: CLRF FE9
00B6: BSF FB8.3
00B8: MOVLW 08
00BA: MOVWF FAF
00BC: MOVLW 02
00BE: MOVWF FB0
00C0: MOVLW A6
00C2: MOVWF FAC
00C4: MOVLW 90
00C6: MOVWF FAB
00C8: MOVF FC1,W
00CA: ANDLW C0
00CC: IORLW 0F
00CE: MOVWF FC1
00D0: MOVLW 07
00D2: MOVWF FB4
00D4: CLRF 18
.................... char n;
....................
.................... n = input(PIN_B0);
00D6: BSF F93.0 // Set TRISB.0 = input pin
00D8: CLRF 19
00DA: BTFSC F81.0 // Read pin B0 and test it.
00DC: INCF 19,F
....................
....................
.................... while(1);
00DE: BRA 00DE |
Here is the test program. It was compiled with vs. 4.083.
| Code: | #include <18F2520.H>
#fuses HS, NOWDT, NOPROTECT, PUT, BROWNOUT, NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#INT_EXT
void ext_isr(void)
{
char c;
c = input(PIN_B0);
}
//=================================
void main()
{
char n;
n = input(PIN_B0);
while(1);
} |
If you still have a problem, then post a very short test program that
demonstrates the problem. |
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