AN247

AN247 A CAN Bootloader for PIC18F CAN Microcontrollers Author: Ross M. Fosler Microchip Technology Inc. The drawback to this is a lack of efficiency, as directly manipulating the target memory and manually verifying data takes significant time on the CAN bus. To make the operation more efficient, the programming target could be given some intelligence, like selfverification. This would make communications unidirectional, essentially cutting the time on the CAN bus in half. Overall, the best savings is to design all the nodes in the system with similar, modular firmware. Each node could then use only those modules required for its task, but the entire group of nodes could be updated simultaneously. The sacrifice here is program memory overhead, since some nodes may have resident firmware that is not used. INTRODUCTION Among the many features built into Microchip’s Enhanced FLASH Microcontroller devices is the capability of the program memory to self-program. This very useful feature has been deliberately included to give the user the ability to perform bootloading operations. Devices like the PIC18F458 are designed with a designated “boot block”, a small section of protectable program memory allocated specifically for bootload firmware. This application note demonstrates a simple bootloader implementation for the PIC18F families of microProgramming a Running System controllers with a CAN module. The goals of this implementation are to stress maximum performance An interestin...