Hi, Following are my questions: 1. I use 128K version of 80C51 and define common area (0-3fff) and 2 other banks. from (4000 - ffff) When I define a font table (array) in one bank. After compilation, I found the common area grows, seems like it relocate the font array into the common area instead of the bank area. 2. I am working on video application, I have a display v-sync interrupt every 1/60 sec. If I stay in this interrupt too long (> 1.5 ~ 2 ms) system hang up. if short delay (1 ms) then everything works fine. Any idea? I know interrupt should be as short as possible but is there any restriction on how long can we stay in interrupt service routine? Really appreciate if someone can help me on these issues. Thanks