Okay, let assume you calculated that refresh routine takes 100ìs.

My refresh routine when calculated, completes in atleast 2000ìs. Can anyone help me to enhance this routine.

To get the speed - and a pleasant scroll - you need a bitmap buffer. A display that scrolls by character rather than row is rather unpleasant to view.

build a buffer of bits that is two messages long, then
again:
start = start of buffer
while (start != (start of buffer + "msg length in rows")
{
display()
start++
}
goto again

Erik