dsPIC30F Family Reference Manual
DS70070B-page 23-40 © 2004 Microchip Technology Inc.
23.6.1.1 Receive Buffer Priority
To provide flexibility, there are several acceptance filters corresponding to each receive buffer.
There is also an implied priority to the receive buffers. RXB0 is the higher priority buffer and has
2 message acceptance filters associated with it. RXB1 is the lower priority buffer and has 4
acceptance filters associated with it. The lower number of possible acceptance filters makes the
match on RXB0 more restrictive and implies the higher priority associated with that buffer.
Additionally, if the RXB0 contains a valid message, and another valid message is received, the
RXB0 can be setup such that it will not overrun and the new message for RXB0 will be placed
into RXB1. Figure 23-8 shows a block diagram of the receive buffer, while Figure 23-9 shows a
flow chart for a receive operation.
Figure 23-8: The Receive Buffers
Acceptance Mask
RXM1
Acceptance Filter
RXF2
Acceptance Filter
RXF3
Acceptance Filter
RXF4
Acceptance Filter
RXF5
R
X
B
1
R
X
B
0
Acceptance Mask
RXM0
Acceptance Filter
RXF0
Acceptance Filter
RXF1
A
c
c
e
p
t
A
c
c
e
p
t
Identifier
Data Field Data Field
Identifier
Message
Assembly
Buffer
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