transfer a string from ROM to an array

[richard]

buff var byte[30] $4f0 ; buff is now straddles banks 4 and 5

_buff 000004F0 symbol table

code still works perfectly as expected

[Marcick]

Richard,
the source of my doubts is that I have some unexpected behaviours and I'm trying to understand where is the problem.
Watching the program memory, I found some "00" chars here and there in the middle of the string
Lets' say the string "Hello",0 when I look the program memory is 48 65 6C 00 6C 6F 00
I'm discovering now that the directive "da" is only for PIC12/16 and not for PIC18

http://ww1.microchip.com/downloads/e...Doc/33014J.pdf

I think I should use "db" or "data", I'm trying to understand

"db" seems to work fine

[richard]

how are you looking at the pgm memory , I think something is not right

for me the da and data directives produce exactly the same result , I left the da directive in, thinking I might try the code on a pic16f1825 for a learning experience , for 7 bit ascii data either will do (pic 18's can store 2x8 bit ,pic 16's 2x7bit )

the relevant listings

0
0013E 6854 7369 6920 00199  data "This is a string",0
          2073 2061 7473 
          6972 676E 0000

00013E 6854 7369 6920 00199  da "This is a string",0
            2073 2061 7473 
            6972 676E 0000

[Marcick]

Found the problem.

I have a string like this:

say "hello"

I use this format do declare it, the same format I was using with arraywrite

@ da "say",34,"hello",34,0

The result in program memory is that before each char 34 is added a char 00
If I use "db" instead the result is correct.
The pdf I linked before says that "da" is not for PIC18

[richard]

where ?
da – Data ASCII.
Generates a packed 14-bit number representing two 7-bit ASCII characters.

[richard]

this works
@ da "say \"Hello\"\0"

[Marcick]

where ?
da – Data ASCII.
Generates a packed 14-bit number representing two 7-bit ASCII characters.

4.14 da – STORE STRINGS IN PROGRAM MEMORY (PIC12/16 MCUs)

Funny, but if you try it you'll see the unwanted 00 added

db is ok

[richard]

db is definitely an easier way to pack a mixed string data statement like "say",34,"hello",34,0 . funny I could never see the point of db until now

[Ruben Pena]

Hi:
I use this routine to send eeprom stored msg's to display LCD.
It can be modified to send then to a string...
I hope this helps...
'************************************************* ***************
'USED VARS:

SDAT VAR PORTD.1 'I2C EEPROM DATA 'ADJUST TO USED PINS AND
SCLK VAR PORTD.0 'I2C EEPROM CLOCK 'MAKE THEM INPUTS IN USED TRIS REG.
CHAR VAR BYTE
SLAVE VAR BYTE
EEADDR VAR WORD
SLAVE = $A0 'EEPROM SLAVE ADDRESS
'***** SUB TO DISPLAY MSGS STORED IN EEPROM ****************
MSG_DISP:
GOSUB CLRDISP 'CLEAR SCREEN
MSG:
LEENXT: I2CREAD SDAT,SCLK,SLAVE,EEADDR,[CHAR] 'SIN CLEAR
IF CHAR => $80 THEN
LCDOUT $FE,CHAR
GOTO INCADD
ENDIF
IF CHAR <> 0 THEN
LCDOUT CHAR
INCADD: EEADDR = EEADDR + 1
GOTO LEENXT
ENDIF
RETURN
'************************************************* *************
'TO CALL THE ROUTINE:
'SET EEPROM ADDRES:
'YOUR STRING CAN HAVE ANY LENGTH AND MUST BE TERMINATED WITH A NULL CHAR
'"00"
'*********************************************
EEADDR = $0350 'WHEREVER YOUR STRING STARTS
GOSUB MSG_DISP
'*********************************************
' YOU MUST USE AN EEPROM WITH WORD ADDRESS (25LC32A,OR BIGGER)
'PROGRAMM YOUR EEPROM WITH MSGS ENDED WITH 00 (NULL) AND TAKE NOTE OF
'THE START ADDRESSES.
'AND THATS ALL...
Greetings...
Ruben de la Pena V.

[HenrikOlsson]

I think it might have something to do with the number of bytes (odd or even) in the string.
In both of Richards examples there's an even number of bytes (16 and 22) but your Hello string there's an odd number of bytes (5). I seem to remember an issue with this being discussed in one of the 'Strings in codespace' threads some years ago.

/Henrik.

[richard]

odd length strings , wastes space but not a problem


00013E 6854 7369 6920 00199 data "This is a string1",0
2073 2061 7473
6972 676E 0031
0000

00013E 6854 7369 6920 00199 da "This is a string1",0
2073 2061 7473
6972 676E 0031
0000

[richard]

00013E 6548 6C6C 006F 00199 da "Hello",0
0000

[richard]

there's another little cheat if all the strings are odd length the 0 terminator is redundant