I encountered a few oddities while writing the graphical LCD code (see Contributions) and a later program, the first two of which I have also emailed, but I am posting the entire set here in case they are of help, or the emails have not got through.
I am using GCB v0.9 3/2/2010 with a copy of UPDATE.ZIP dated/downloaded 5th April.
My program contains the following GCB variable declaration and subroutine. It is being compiled with a #chip 16F873A, 4 directive.
DIM GLCD_gen0 AS BYTE ' general variable used for calculations (eg column addresses), loops, etc
....
SUB GLCD_serial(oct)
FOR GLCD_gen0 = 1 TO 8
SET GLCD_SCLK OFF ' ensure clock line is low
SET GLCD_SID OFF ' set data bit to be sent as 0
{ IF statement goes here - see below }
SET GLCD_SCLK ON ' clock bit into module on rising edge of clock line
ROTATE oct LEFT SIMPLE ' move to next bit
NEXT
SET GLCD_SCLK OFF ' ensure clock line is low
EXIT SUB
The part that is generating assembler that I don't understand is the IF statement in the middle of this routine which is intended to test bit 7 of the variable and set an output port accordingly.
On other BASICs I have used in the past there is an implied "<> 0" for any IF condition. But when I use:
This appears to be ANDing the contents of OCT with 255 and testing bit 0 of the result (I don't understand this at all, but I don't believe it will do what I want it to do)
I then guessed that this was an operator precedence error and tried this version of the IF statement:
IF (oct AND b'10000000') > 0 THEN SET GLCD_SID ON
This gives what looks to me to be assembler that will do what I need it to do:
I encountered a few oddities while writing the graphical LCD code (see Contributions) and a later program, the first two of which I have also emailed, but I am posting the entire set here in case they are of help, or the emails have not got through.
I am using GCB v0.9 3/2/2010 with a copy of UPDATE.ZIP dated/downloaded 5th April.
My program contains the following GCB variable declaration and subroutine. It is being compiled with a #chip 16F873A, 4 directive.
DIM GLCD_gen0 AS BYTE ' general variable used for calculations (eg column addresses), loops, etc .... SUB GLCD_serial(oct) FOR GLCD_gen0 = 1 TO 8 SET GLCD_SCLK OFF ' ensure clock line is low SET GLCD_SID OFF ' set data bit to be sent as 0 { IF statement goes here - see below } SET GLCD_SCLK ON ' clock bit into module on rising edge of clock line ROTATE oct LEFT SIMPLE ' move to next bit NEXT SET GLCD_SCLK OFF ' ensure clock line is low EXIT SUBThe part that is generating assembler that I don't understand is the IF statement in the middle of this routine which is intended to test bit 7 of the variable and set an output port accordingly.
On other BASICs I have used in the past there is an implied "<> 0" for any IF condition. But when I use:
IF oct AND b'10000000' THEN SET GLCD_SID ON
The compiler generates the assembler:
GLCD_SERIAL clrf GLCD_GEN0 SysForLoop1 incf GLCD_GEN0,F bcf PORTB,2 bcf PORTB,1 movf OCT & B'10000000',F btfss STATUS,Z bsf PORTB,1 bsf PORTB,2 rlf OCT,W rlf OCT,F movlw 8 subwf GLCD_GEN0,W btfss STATUS, C goto SysForLoop1 bcf PORTB,2 return returnWhich appears to be ANDing the address of OCT with 128 and putting the result in F (have I got that right?)
I presumed that this was because a specific test for "> 0" had to be included, so I tried:
IF oct AND b'10000000' > 0 THEN SET GLCD_SID ON
This gives the assembler:
GLCD_SERIAL clrf GLCD_GEN0 SysForLoop1 incf GLCD_GEN0,F bcf PORTB,2 bcf PORTB,1 movlw 255 andwf OCT,W movwf SysTemp1 btfsc SysTemp1,0 bsf PORTB,1 bsf PORTB,2 rlf OCT,W rlf OCT,F movlw 8 subwf GLCD_GEN0,W btfss STATUS, C goto SysForLoop1 bcf PORTB,2 return returnThis appears to be ANDing the contents of OCT with 255 and testing bit 0 of the result (I don't understand this at all, but I don't believe it will do what I want it to do)
I then guessed that this was an operator precedence error and tried this version of the IF statement:
IF (oct AND b'10000000') > 0 THEN SET GLCD_SID ON
This gives what looks to me to be assembler that will do what I need it to do:
GLCD_SERIAL clrf GLCD_GEN0 SysForLoop1 incf GLCD_GEN0,F bcf PORTB,2 bcf PORTB,1 movlw 128 andwf OCT,W movwf SysTemp1 movwf SysCalcTempB clrf SysCalcTempA call SysCompLessThan btfsc SysCalcTempX,0 bsf PORTB,1 bsf PORTB,2 rlf OCT,W rlf OCT,F movlw 8 subwf GLCD_GEN0,W btfss STATUS, C goto SysForLoop1 bcf PORTB,2 return returnAs you would expect the statement:
IF oct.7 ON THEN SET GLCD_SID ON
also works entirely correctly (and more efficiently, of course) and is the version I should have used from the start.
GLCD_SERIAL clrf GLCD_GEN0 SysForLoop1 incf GLCD_GEN0,F bcf PORTB,2 bcf PORTB,1 btfsc OCT,7 bsf PORTB,1 bsf PORTB,2 rlf OCT,W rlf OCT,F movlw 8 subwf GLCD_GEN0,W btfss STATUS, C goto SysForLoop1 bcf PORTB,2 return return(Not sure about the double "return" though…)
Mark