MCP2515-E/PRB2 Microchip Technology, MCP2515-E/PRB2 Datasheet - Page 58

• Manufacturer Part Number: MCP2515-E/PRB2
• Description: CAN controller with SPI interface, 125 deg C, -40C to +125C, 18-PDIP, TUBE
• Manufacturer: Microchip Technology

MCP2515
10.4
Loopback mode will allow internal transmission of
messages from the transmit buffers to the receive
buffers without actually transmitting messages on the
CAN bus. This mode can be used in system
development and testing.
In this mode, the ACK bit is ignored and the device will
allow incoming messages from itself just as if they were
coming from another node. The Loopback mode is a
silent mode, meaning no messages will be transmitted
while in this state (including error flags or acknowledge
signals). The TXCAN pin will be in a recessive state.
The filters and masks can be used to allow only
particular messages to be loaded into the receive
registers. The masks can be set to all zeros to provide
a mode that accepts all messages. The Loopback
mode is activated by setting the mode request bits in
the CANCTRL register.
REGISTER 10-1:
DS21801E-page 58
bit 7
Legend:
R = Readable bit
-n = Value at POR
bit 7-5
bit 4
bit 3
bit 2
bit 1-0
REQOP2
R/W-1
Loopback Mode
REQOP: Request Operation Mode bits <2:0>
000 = Set Normal Operation mode
001 = Set Sleep mode
010 = Set Loopback mode
011 = Set Listen-only mode
100 = Set Configuration mode
All other values for REQOP bits are invalid and should not be used
On power-up, REQOP = b’111’
ABAT: Abort All Pending Transmissions bit
1 = Request abort of all pending transmit buffers
0 = Terminate request to abort all transmissions
OSM: One Shot Mode bit
1 = Enabled. Message will only attempt to transmit one time
0 = Disabled. Messages will reattempt transmission, if required
CLKEN: CLKOUT Pin Enable bit
1 = CLKOUT pin enabled
0 = CLKOUT pin disabled (Pin is in high-impedance state)
CLKPRE: CLKOUT Pin Prescaler bits <1:0>
00 = F
01 = F
10 = F
11 = F
REQOP1
R/W-0
CANCTRL – CAN CONTROL REGISTER
(ADDRESS: XFh)
CLKOUT
CLKOUT
CLKOUT
CLKOUT
W = Writable bit
‘1’ = Bit is set
= System Clock/1
= System Clock/2
= System Clock/4
= System Clock/8
REQOP0
R/W-0
R/W-0
ABAT
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
R/W-0
10.5
Normal mode is the standard operating mode of the
MCP2515. In this mode, the device actively monitors all
bus messages and generates acknowledge bits, error
frames, etc. This is also the only mode in which the
MCP2515 will transmit messages over the CAN bus.
OSM
Normal Mode
CLKEN
R/W-1
© 2007 Microchip Technology Inc.
x = Bit is unknown
CLKPRE1
R/W-1
CLKPRE0
R/W-1
bit 0