Hi, finally I was able to clear all the clouds.


>         BSF     INTCON, GIE             ; Again, is this code necessary?

This is one of the pitfalls. Thanks Olin, as well as Omer. I thinks this the
reason why the PIC ran for some time, and then halted. I was introducing a
nested interrupt, and the stack was trashed.

The second pitfall is the paging problem.

HEX2ASC
;***************************************************************************
***
; Description: Convert W lower 4 bits to ASCII table defined in HD44780
;
; B7 B6 B5 B4 B3 B2 B1 B0
;  x  x  x  x B3 B2 B1 B0
;
; Conditions: Value to be converted in W (4 LSB)
; Result of conversion (8-bits) in W
;
;***************************************************************************
***
        ANDLW   0x0F
        MOVWF   W0
        MOVLW   HIGH TABLE_ASCII
        MOVWF   PCLATH
        MOVLW   LOW TABLE_ASCII
        ADDWF   W0, W
        SKPNC
        INCF    PCLATH, F
        MOVWF   PCL
TABLE_ASCII     RETLW   0x30    ; '0'
        RETLW   0x31    ; '1'
        RETLW   0x32    ; '2'
        RETLW   0x33    ; '3'
        RETLW   0x34    ; '4'
        RETLW   0x35    ; '5'
        RETLW   0x36    ; '6'
        RETLW   0x37    ; '7'
        RETLW   0x38    ; '8'
        RETLW   0x39    ; '9'
        RETLW   0x41    ; 'A'
        RETLW   0x42    ; 'B'
        RETLW   0x43    ; 'C'
        RETLW   0x44    ; 'D'
        RETLW   0x45    ; 'E'
        RETLW   0x46    ; 'F'

Originally that is only 'ANDLW 0x0F' and 'ADDWF PCL, F' instead of the first
9 line of codes.

When I was first writing this code, it stay below 0x100 of page 0. As codes
are added little by little, it is pushed out the 0x100 boundary. One
question is will this codes work in pages other than page 0? Of course then
I have to use the FCALL macro, but will this code work without effecting
other paging issue.

Jan, I thinks this is the reason I get funny things shown in LCD. Thanks a
lot for your response.

Regards,

WH Tan

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