Hi All,
I am studying the PIC, and plan to write some code for ham radio. :)
Here I am confused when I wrote code for table looking up. The PIC I
will use is 16C73. The code as following:
(A)
                org     0
START:          bsf     pclath,3
                movlw   0
                movwf   INDEX
                call    GET_TAB_ITEM
                ...

                org     0xE00
TAB_LOOKUP:     movwf   pcl                     /*********************/

GET_TAB_ITEM:   movlw   0x0F
                movwf   pclath
                movf    INDEX,w
                call    TAB_LOOKUP
                return

                org     0xF00
                dt      0,1,2,3,........
(B)
                org     0
START:          bsf     pclath,3
                movlw   0
                movwf   INDEX
                call    GET_TAB_ITEM
                ...

                org     0xE00
TAB_LOOKUP:     addwf   pcl,f                   /*********************/

GET_TAB_ITEM:   movlw   0x0F
                movwf   pclath
                movf    INDEX,w
                call    TAB_LOOKUP
                return

                org     0xF00
                dt      0,1,2,3,........

You can see the code (A) and (B), the only difference betweeb them is
the line marked with /***/, personally I think in code <A> and <B>
[addwf pcl,f] will get the same result to [movwf pcl], but when I use
the MPLAB to simulate the result, it is different, <A> returns 0, but
<B> returns 1. Why?

Merry XMAS and Happy BOXING DAY!


Jerry Meng, BA1FB

mailto:ba1fb@amsat.org
http://www.srsnet.com/~ba1fb