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
BUFFERS
Acceptance Mask
RXM1
Acceptance Filter
RXF2
TXB0
MESSAGE
TXREQ
ABTF
MLOA
TXERR
TXB1
MESSAGE
TXREQ
ABTF
MLOA
TXERR
TXB2
MESSAGE
TXREQ
ABTF
MLOA
TXERR
A
c
c
e
p
t
Acceptance Mask
RXM0
Acceptance Filter
RXF0
Acceptance Filter
RXF1
R
X
B
0
Acceptance Filter
RXF3
Acceptance Filter
RXF4
Acceptance Filter
RXF5
R
X
B
1
A
c
c
e
p
t
Message
Queue
Control
Identifier
M
A
B
Identifier
Transmit Byte Sequencer
Data Field
Data Field
PROTOCOL
ENGINE
Receive
Error
Counter
Transmit
Error
Counter
REC
TEC
ErrPas
BusOff
Transmit<7:0>
Shift<14:0>
{Transmit<5:0>, Receive<8:0>}
Comparator
Receive<7:0>
CRC<14:0>
Protocol
Finite
State
Machine
SOF
Transmit
Logic
Bit
Timing
Logic
Clock
Generator
TX
RX
Configuration
Registers
©
2005 Microchip Technology Inc.
Preliminary
DS21801D-page 5
MICROCHIP [ MICROCHIP TECHNOLOGY ]
