Книга: Advanced PIC Microcontroller Projects in C

9.9.7 CAN Message Transmission 

9.9.7 CAN Message Transmission 

The PIC18F258 microcontroller implements three dedicated transmit buffers: TXB0, TXB1, and TXB2. Pending transmittable messages are in a priority queue. Before the SOF is sent, the priorities of all buffers queued for transmission are compared. The transmit buffer with the highest priority is sent first. If two buffers have the same priority, the one with the higher buffer number is sent first. There are four levels of priority.