CP3BT23_14 Datasheet, PDF (164/324 Pages) Texas Instruments – CP3BT23 Reprogrammable Connectivity Processor with Bluetooth and Dual CAN Interfaces

CP3BT23
SNOSCX3A – JULY 2013 – REVISED JANUARY 2014
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18.10.17 CAN Timer Register (CTMRn)
The CTMRn register reports the current value of the Time Stamp Counter as described in Section 18.8.
15
0
CTMR15:0
0
R
The CTMRn register is a free running 16-bit counter. It contains the number of CAN bits recognized by the
CAN module since the register has been cleared. The counter starts to increment from the value 0000b
after a hardware reset. If the Timer Stamp Enable bit (TSTPEN) in the CGCRn register is set, the counter
will also be cleared on a message transfer of the message buffer 0.
The contents of CTMR are captured into the Time Stamp register of the message buffer after successfully
sending or receiving a frame, as described in Section 18.8.
18.11 SYSTEM START-UP AND MULTI-INPUT WAKE-UP
After system start-up, all CAN-related registers are in their reset state. The CAN module can be enabled
after all configurations are set to ??? ing initial settings must be made:
• Configure the CAN Timing register (CTIM). See Section 18.11.4.
• Configure every buffer to its function as receive/transmit. See Section 18.10.1.
• Set the acceptance filtering masks. See Section 18.4.
• Enable the CAN interface. See Section 18.10.6.
Before disabling the CAN module, software must make sure that no transmission is still pending.
Note: Activity on the CAN bus can wake up the device from a reduced-power mode by selecting the
CANnRX pin as an input to the Multi-Input Wake-Up module. In this case, the CAN module must not be
disabled before entering the reduced-power mode. Disabling the CAN module also disables the CANnRX
pin. As an alternative, the CANnRX pin can be connected to any other input pin of the Multi-Input Wake-
Up module. This input channel must then be configured to trigger a wake-up event on a falling edge (if a
dominant bit is represented by a low level). In this case, the CAN module can be disabled before entering
the reduced-power mode. After waking up, software must enable the CAN module again. All configuration
and buffer registers still contain the same data they held before the reduced-power mode was entered.
18.11.1 External Connection
The CAN module uses the CANnTX and CANnRX pins to connect to the physical layer of the CAN
interface. They provide the functionality described in Table 18-21.
Signal Name
CANnTX
CANnRX
Table 18-21. External CAN Pins
Type
Output
Input
Description
Transmit data to the CAN bus
Receive data from the CAN bus
The logic levels are configurable by the CTX and CRX bits of the Global Configuration Register CGCRn
(see Section 18.10.6).
164 CAN Module
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