I would like to set a (fuse?) bit to select the external Flash/PEROM as program memory instead of default Flash internal to the AT89C51. Is the BLJB bit the one I want to set? How do I set it?
"The BLJB bit is in the Hardware Security Byte; ergo, you must use a programer option to set it. Is that not clear?" It's plain wrong. It can be modified by software.