> If all communication timing are ok then only Vlc must modify
> the contrast

Two jobs ago the LCD I used had Vlc tied to 0V. I snipped the LCD
routines from a previous project (which worked fine) and included
them into the new one. The LCD contrast would not initialise until
I pressed the reset key. On power-up the background to the chars
on the LCD was very dark, and cleared only after a reset. Before I
got to figure out what was wrong I needed to change the xtal from
4MHz to 16MHz. After the init timing was amended to suit 16MHz
it worked perfectly. So the conclusion is.........s/w or h/w problem
on the original ??? A bit of both ??? The routines came from a 4MHz
program which should have not misbehaved in another 4MHz PIC

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