Post by thread:No More PCLATH Problems

Hello All, Well thanks to Andy Warren and indeed all the members of the PICLIST who sent replies to my PCLATH problem, I have finally managed to get my code to work; I can now reliably cross page boundaries when processing long text strings - brilliant. The problem was actually in the write_string subroutine which Andy managed to spot; I would have never thought to modify the PCLATH register here since the number of entries in the 'jump table' was so little in comparison with the those of the actual text string look-up tables. Actually the code which I recently sent to PICLIST was in fact the wrong version; I have been struggling so much attempting to solve the problem that I ended up at the stage where I was 'trying anything' without really thinking, and in my panic I sent a version which incorrectly included the BSF PCLATH,0. Just in case anyone on the list incorrectly thinks that the exclusion of this instruction was the solution to my problem, then I have included the subroutines of my working code. As I become more proficient with the PIC assembly language, I will make a positive effort to help other members of the PICLIST solve their problems. Many thanks to all members, and best wishes: Lee Hewitt (Manchester ENGLAND) write_string clrf char_ptr ;Clear character pointer to zero movwf msg_ptr ;Load message pointer with message number ws1: movlw high (JUMP_TABLE) movwf PCLATH clrc ;Clear carry 'f lag in status register' rlf msg_ptr,w ;Multiply by two to prevent pointing to goto addlw low (JUMP_TABLE) ;Computed GOTO string pointer btfsc STATUS,C incf PCLATH,f movwf PCL JUMP_TABLE: call string0 ;Get next character in the string goto ws2 ;Upon return call ws2 to step through characters call string1 goto ws2 call string2 goto ws2 call string3 goto ws2 call string4 goto ws2 call string5 goto ws2 call string6 ;fall into ws2 upon return ws2: movwf temp1 ;store char returned from table in temp1 xorlw EOMSG ;test for end of message marker (0x04) btfsc ZERO ;Zero set iff EOM is detected return ;End Of Message marker detected, thu s return movf temp1,w xorlw EOLN ;Test for EOL marker btfsc ZERO goto new_line_1 movf temp1,w call send_lcd_char tst incf char_ptr,f goto ws1 new_line_1 movlw NW_LINE ;send new line command to display call send_lcd_cmd call short_delay goto tst ;Text string look-up tables string0 bcf PCLATH,0 movlw high (TABLE_0) ;Load HIGH byte movwf PCLATH movlw low (TABLE_0) ;Load LOW byte addwf char_ptr,w btfsc STATUS,C incf PCLATH,f movwf PCL TABLE_0 dt "*** Power On ***",EOLN," Master Reset ",EOMSG string1 bcf PCLATH,0 movlw high (TABLE_1) ;Load HIGH byte movwf PCLATH movlw low (TABLE_1) ;Load LOW byte addwf char_ptr,w btfsc STATUS,C INCF PCLATH,f movwf PCL TABLE_1 dt "Waiting For SOH",EOLN,"From Host PC ...",EOMSG string2 bcf PCLATH,0 movlw high (TABLE_2) ;Load HIGH byte movwf PCLATH movlw low (TABLE_2) ;Load LOW byte addwf char_ptr,w btfsc STATUS,C INCF PCLATH,f movwf PCL TABLE_2 dt " Connection Has ",EOLN,"Been Established",EOMSG string3 bcf PCLATH,0 movlw high (TABLE_3) ;Load HIGH byte movwf PCLATH movlw low (TABLE_3) ;Load LOW byte addwf char_ptr,w btfsc STATUS,C INCF PCLATH,f movwf PCL TABLE_3 dt "Waiting For STX",EOLN,"From Host PC ...",EOMSG string4 bcf PCLATH,0 movlw high (TABLE_4) ;Load HIGH byte movwf PCLATH movlw low (TABLE_4) ;Load LOW byte addwf char_ptr,w btfsc STATUS,C INCF PCLATH,f movwf PCL TABLE_4 dt "Receiving Config",EOLN," Data From Host ",EOMSG string5 bcf PCLATH,0 movlw high (TABLE_5) ;Load HIGH byte movwf PCLATH movlw low (TABLE_5) ;Load LOW byte addwf char_ptr,w btfsc STATUS,C INCF PCLATH,f movwf PCL TABLE_5 dt "Waiting For EOT",EOLN,"From Host PC ...",EOMSG string6 bcf PCLATH,0 movlw high (TABLE_6) ;Load HIGH byte movwf PCLATH movlw low (TABLE_6) ;Load LOW byte addwf char_ptr,w btfsc STATUS,C INCF PCLATH,f movwf PCL TABLE_6 dt " Data Transfer ",EOLN," *** Complete ***",EOMSG ******* End Of Program *******

Lee Hewitt wrote: > Hello All, > Well thanks to Andy Warren and indeed all the members of the > PICLIST who sent replies to my PCLATH problem, I have finally managed to get > my code to work; I can now reliably cross page boundaries when processing > long text strings - brilliant. Yes, I'm sure this is one piece of code you wont forget soon <G>! > Actually the code which I recently sent to PICLIST was in fact the > wrong version; I have been struggling so much attempting to solve the problem > that I ended up at the stage where I was 'trying anything' without really > thinking, ...argh! Been there too :-( > and in my panic As I become more proficient with the PIC assembly language, I will > make a positive effort to help other members of the PICLIST solve their > problems. > Oooh I can think of a couple... one of which is my re-surfacing LCD trouble...... Cheers! -- Eric van Es | Cape Town, South Africa spam_OUTvanesTakeThisOuTilink.nis.za | http://www.nis.za/~vanes LOOKING FOR TEMPORARY / HOLIDAY ACCOMODATION? http://www.nis.za/~vanes/accom.htm