Datasheet

© 2007 Microchip Technology Inc. DS21801E-page 5
MCP2515
1.4 Transmit/Receive Buffers/Masks/
Filters
The MCP2515 has three transmit and two receive
buffers, two acceptance masks (one for each receive
buffer) and a total of six acceptance filters. Figure 1-3
shows a block diagram of these buffers and their
connection to the protocol engine.
FIGURE 1-3: CAN BUFFERS AND PROTOCOL ENGINE BLOCK DIAGRAM
Acceptance Filter
RXF2
R
X
B
1
Identifier
Data Field Data Field
Identifier
Acceptance Mask
RXM1
Acceptance Filter
RXF3
Acceptance Filter
RXF4
Acceptance Filter
RXF5
M
A
B
Acceptance Filter
RXF0
Acceptance Filter
RXF1
R
X
B
0
TXREQ
TXB2
ABTF MLOA TXERR MESSAGE
Message
Queue
Control
Transmit Byte Sequencer
TXREQ
TXB0
ABTF MLOA TXERR MESSAGE
CRC<14:0>
Comparator
Receive<7:0>Transmit<7:0>
Receive
Error
Transmit
Error
Protocol
REC
TEC
ErrPas
BusOff
Finite
State
Machine
Counter
Counter
Shift<14:0>
{Transmit<5:0>, Receive<8:0>}
Transmit
Logic
Bit
Timing
Logic
TX RX
Configuration
Registers
Clock
Generator
PROTOCOL
ENGINE
BUFFERS
TXREQ
TXB1
ABTF MLOA TXERR MESSAGE
Acceptance Mask
RXM0
A
c
c
e
p
t
A
c
c
e
p
t
SOF