PIC18F2480/2580/4480/4580
The transmit buffer with the highest priority will be sent
first. If two buffers have the same priority setting, the
buffer with the highest buffer number will be sent first.
There are four levels of transmit priority. If the TXP bits
for a particular message buffer are set to ‘11’, that buf-
fer has the highest possible priority. If the TXP bits for
a particular message buffer are set to ‘00’, that buffer
has the lowest possible priority.
24.6.3
TRANSMIT PRIORITY
prioritization within the
Transmit priority is
a
PIC18F2480/2580/4480/4580 devices of the pending
transmittable messages. This is independent from and
not related to any prioritization implicit in the message
arbitration scheme built into the CAN protocol. Prior to
sending the Start-Of-Frame (SOF), the priority of all
buffers that are queued for transmission is compared.
FIGURE 24-2:
TRANSMIT BUFFERS
TXB0
TXB1
TXB2
TXB3 - TXB8
Message
Queue
Control
Transmit Byte Sequencer
DS39637D-page 334
© 2009 Microchip Technology Inc.
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