Ascii chars are only 7 bits if doing a table read on a chr $ then set =
bit 7
to 1 for the terminate char and test for that (unless you are doing jap
chrs)that will save a byte per string assy below extract from lcd driver
that cant send funny chars bits in >> >> does the check for end of =
string

Steve...

        MOVWF   STRNUM          ; SAVE STRING NUMBER
        MOVLW   0FFH            ; POINTER TO BEGINING OF STRING
        MOVWF   TABOFF          ; WELL IT IS NOW
DOSTR   PAGE1                   ; SET PAGE MARKER
        CALL    CALLSTR         ; GET STRING CHAR POINTED TO IN TABOFF
        PAGE0                   ; RESET PAGE MARKER
>>
        MOVWF   LCDCH           ; SAVE CHAR
        ANDLW   B'01111111'     ; MASK END BIT (END OF STRING MARKER)
        CALL    LCD_OUT         ; SEND CHAR
        BTFSS   LCDCH,7         ; CHECK LAST
        GOTO    DOSTR           ; NOT FINISHED DO SOME MORE
>>
        RETLW   0               ; EXIT
-----Original Message-----
From: pic microcontroller discussion list =
[mailto:PICLIST@MITVMA.MIT.EDU] On
Behalf Of Spehro Pefhany
Sent: 22 July 2003 21:13
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: Out of ROM PIC18F452 ....what do to?


At 08:07 PM 7/22/2003 +0100, you wrote:
>Are C compilers intelligent enough to convert Print "HELLO ALL" to a=20
>data table and then read that data back from the table or do they=20
>convert it to:-

Strings in standard C are stored as a null-terminated array of char, so =
your
"HELLO ALL" would take (at least) 10 bytes (9 for the characters plus 1 =
for
the terminating null). It might take more, especially on a >8 bit =
processor.

The parameter to the print routine would be a pointer to const char, in
other words, the address in program memory where the string begins.

The print routine (eg. cputs ) would just grab a character, terminate if
it's a null, otherwise print it, increment the local copy of the =
pointer,
and repeat.

So a const string declaration would look like this:

const char hello[]=3D "HELLO ALL";  , which would use 10 bytes of FLASH. =
It
may or may not be padded up to the next even byte.

..the print statement would be something like cputs(hello);

The call would be the same number of bytes regardless of the length of =
the
string.



You could, and probably would, write it just about the same way in =
assembly,
of course. This is the kind of stuff that C does very well.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the
reward"
speff@interlog.com             Info for manufacturers: =
http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  =
http://www.speff.com

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