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MOTOROLA
Chapter 16. CAN 2.0B Controller Module
16-13
TouCAN Operation
16.4 TouCAN Operation
The basic operation of the TouCAN can be divided into four areas:
Reset
Initialization of the module
Transmit message handling
Receive message handling
Example sequences for performing each of these processes is given in the following
paragraphs.
16.4.1
TouCAN Reset
The TouCAN can be reset in two ways:
Hard reset of the module via SRESET.
Soft reset of the module, using the SOFTRST bit in the module configuration
register
Following the negation of reset, the TouCAN is not synchronized with the CAN bus, and
the HALT, FRZ, and FRZACK bits in the module configuration register are set. In this state,
the TouCAN does not initiate frame transmissions or receive any frames from the CAN bus.
The contents of the message buffers are not changed following reset.
Any configuration change or initialization requires that the TouCAN be frozen by either the
assertion of the HALT bit in the module configuration register or by reset.
16.4.2
TouCAN Initialization
Initialization of the TouCAN includes the initial configuration of the message buffers and
configuration of the CAN communication parameters following a reset, as well as any
reconfiguration which may be required during operation. The following is a general
initialization sequence for the TouCAN:
1. Initialize all operation modes
a) Initialize the transmit and receive pin modes in CANCTRL0
b) Initialize the bit timing parameters PROPSEG, PSEGS1, PSEG2, and RJW in
CANCTRL1 and CANCTRL2
c) Select the S-clock rate by programming the PRESDIV register
d) Select the internal arbitration mode (LBUF bit in CANCTRL1)
2. Initialize message buffers
a) The control/status word of all message buffers must be written either as an
active or inactive message buffer.
b) All other entries in each message buffer should be initialized as required