AN440

www.DataSheet4U.com Philips Semiconductors Microcontroller Products Application note RAM loader program for 80C51 family applications Author: Greg Goodhue The following program allows an 80C51 family microcontroller to load most of its code into a RAM over a serial link after power up and execute out of the RAM for normal operation. This can allow a final product to have firmware updates done by a simple diskette mailing. Such a program is often called a “bootstrap loader”. For this example, it is assumed that the code download is done via a serial communication link, although the program could be adapted to other forms of download. The comments at the beginning of the listing are intended to document the program and its use completely. An additional comment would be that any static routines (low level routines that are unlikely to change over time) can probably be put into the permanent program memory (on-chip or off-chip ROM or EPROM) along AN440 with the bootstrap loader to save program RAM space for other things. The source code file for this program is available for downloading from the Philips computer bulletin board system. This system is open to all callers, operates 24 hours a day, and can be accessed with modems at 2400, 1200, and 300 baud. The telephone numbers for the BBS are: (800) 451-6644 (in the U.S. only) or (408) 991-2406. Basic Diagram of RAM Connections for the Boot Loader 80/87C51 containing the boot loader program (or use external EPROM) Program RA...