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| Author |
Message |
rob
Guest
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| bit test problem |
 Posted: Wed Feb 09, 2005 5:51 am |
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Hi to all.
I have a small issue with the bit_test() function I hope someone can help me with.
Sometimes the bit_test fuction does not work as I would expect.
here is an example.
| Code: |
include <16F876.h>
#byte portb = 6
int a;
void main()
{
if(bit_test(portb,4)) a = 6;
if(bit_test(portb,4)==1) a =7;
} |
Largest free fragment is 2048
RAM used: 7 (4%) at main() level
7 (4%) worst case
Stack: 0 locations
*
0000: MOVLW 00
0001: MOVWF 0A
0002: GOTO 004
0003: NOP
.................... #include <16F876.h>
.................... //////// Standard Header file for the PIC16F876 device ////////////////
.................... #device PIC16F876
.................... #list
....................
....................
.................... #byte portb = 6
.................... int a;
....................
.................... void main()
.................... {
0004: CLRF 04
0005: MOVLW 1F
0006: ANDWF 03,F
0007: BSF 03.5
0008: BSF 1F.0
0009: BSF 1F.1
000A: BSF 1F.2
000B: BCF 1F.3
.................... if(bit_test(portb,4)) a = 6;
000C: BCF 03.5
000D: BTFSS 06.4
000E: GOTO 011
000F: MOVLW 06
0010: MOVWF 20
....................
.................... if(bit_test(portb,4)==1) a =7;
0011: BTFSS 06.0
0012: GOTO 015
0013: MOVLW 07
0014: MOVWF 20
....................
.................... }
....................
0015: SLEEP
In the first bit_test the generated code is correct , but in the second , the compiler always generates a test of bit 0. Why is this.
I am using 3.207. A friend of mine is using a earlier version and that version does not do this.
Any ideas.
Cheers
Rob |
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Humberto
Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata
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| Posted: Wed Feb 09, 2005 8:12 am |
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The function bit_test test the specified bit if it is SET/TRUE or CLEAR/FALSE
| Quote: |
if(bit_test(portb,4)==1)
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doesnīt have any sense, ==1 it is out of the function scope and should give a syntax error.
Humberto |
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rob
Guest
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| Posted: Wed Feb 09, 2005 8:39 am |
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Hi there.
What you say makes sence , but the compiler does not give any warnings :0(
Also , did not happen in previous versions.
cheers
Rob |
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Humberto
Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata
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| Posted: Wed Feb 09, 2005 9:08 am |
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Hi Rob,
Yep, just tested and it didnīt give any warning mssge. Just ignore it.
It seems something wrong with the compiler version 3.207
| Quote: |
.................... if(bit_test(portb,4)==1) a =7;
0011: BTFSS 06.0
0012: GOTO 015
0013: MOVLW 07
0014: MOVWF 20
....................
|
Version 3.216 give the following:
| Quote: |
.................... if(bit_test(portb,4)==1) a =7;
0011: BTFSS 06.4
0012: GOTO 015
0013: MOVLW 07
0014: MOVWF 20
|
Humberto |
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Radix
Guest
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| Posted: Wed Feb 09, 2005 9:20 am |
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Version 3.179 gives the following:
| Code: | .................... if(bit_test(portb,4)) a = 6;
000A: BCF 03.5
000B: BTFSS 06.4
000C: GOTO 00F
000D: MOVLW 06
000E: MOVWF 20
|
| Code: | .................... if(bit_test(portb,4)==1) a =7;
000F: MOVLW 00
0010: BTFSC 06.4
0011: MOVLW 01
0012: SUBLW 01
0013: BTFSS 03.2
0014: GOTO 017
0015: MOVLW 07
0016: MOVWF 20
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And as far as I'm concerned works okay. 
But if the latest version is erratic, please be so kind to report this to CCS.  (Though I will not profit from it since my maintenance ran out  ) |
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Guest
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| Posted: Sat Feb 12, 2005 2:11 am |
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| Humberto wrote: | | It seems something wrong with the compiler version 3.207 |
It is a bug in 3.207 listed here: http://www.ccsinfo.com/versions.shtml
3.208 A bug involving (bit_test(...)==x) is fixed |
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