Post by thread:[PIC]:understanding code for a newbie

Hi, could anyone explain to me how this code works? Thanks in advance MnLoop clrf MessPt movlw 0x80 ; line 1 call LCDins Loop1 call TheText xorlw 0h btfsc STATUS,Z goto DoLine2 call LCDout incf MessPt goto Loop1 DoLine2 incf MessPt movlw 0xC0 ; line 2 call LCDins Loop2 call TheText xorlw 0h btfsc STATUS,Z goto DoDelay call LCDout incf MessPt goto Loop2 DoDelay call BigDel ; wait goto MnLoop -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

>Hi, could anyone explain to me how this code works? >Thanks in advance This is an example of what I might consider "poor commenting" :) Why, and I emphasize *WHY*, don't people comment their damn code? I have enough trouble trying to figure out my own code that I wrote last year, let alone new code that I happen to find on the internet. Fortunately, this is simple enough. It is LCD message code. Basically, it calls one lookup table containing messages to output to the LCD, separated by zeroes, and sends them to lines 1 and 2 of the display. There is no LCD initialization here, nor are there any actual messages (among other things) so this code wouldn't work in and of itself. ------------------------------------ >MnLoop clrf MessPt > movlw 0x80 ; line 1 > call LCDins The above code sets the message pointer MessPt to the beginning of the message table, and sends 0x80 to the LCD as an instruction to move the cursor to column 0 of the first line. >Loop1 call TheText > xorlw 0h > btfsc STATUS,Z > goto DoLine2 > call LCDout > incf MessPt > goto Loop1 The above code looks for a table with a label "TheText" and returns one character at a time until a value of 0x00 is found at the end of the first message. >DoLine2 incf MessPt > movlw 0xC0 ; line 2 > call LCDins The above code does the same as the initial code, except positions the cursor at column 0 of the second LCD line. >Loop2 call TheText > xorlw 0h > btfsc STATUS,Z > goto DoDelay > call LCDout > incf MessPt > goto Loop2 The above code does the same as the previous code loop. Note that the message pointer has been incremented at the DoLine2 label, advancing past the first "0x00" found in the message table. This loop then calls the same message table "TheText" and outputs each character to the LCD until the second "0x00" is found in the table. >DoDelay call BigDel ; wait > goto MnLoop Wait and return to do this entire thing again. Note that the display is not cleared, so each message will simply overwrite the previous message. --Andrew _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.