dsPIC30F Family Reference Manual
DS70070B-page 23-38 © 2004 Microchip Technology Inc.
23.5.5 Configuration Mode
In the Configuration mode, the module will not transmit or receive. The error counters are cleared
and the interrupt flags remain unchanged. The programmer will have access to configuration
registers that are access restricted in other modes.
After a device Reset the CAN module is in the Configuration mode (OPMODE<2:0> = ‘100’). The
error counters are cleared and all registers contain the Reset values. It should be ensured that
the initialization is performed before REQOP<2> bit is cleared.
The CAN module has to be initialized before its activation. This is only possible if the module is
in the Configuration mode. The Configuration mode is requested by setting the REQOP<2> bit.
Only when the Status bit OPMODE<2> has a high level, the initialization can be performed.
Afterwards the configuration registers and the acceptance mask registers and the acceptance
filter registers can be written. The module is activated by clearing the control bits REQOP<2:0>.
The module will protect the user from accidentally violating the CAN protocol through program-
ming errors. All registers which control the configuration of the module can not be modified while
the module is on-line. The CAN module will not be allowed to enter the Configuration mode while
a transmission is taking place. The Configuration mode serves as a lock to protect the following
registers.
• All Module Control Registers
• Baud Rate and Interrupt Configuration Registers
• Bus Timing Registers
• Identifier Acceptance Filter Registers
• Identifier Acceptance Mask Registers
23.5.6 Listen All Messages Mode
Listen All Messages mode is a special case of Normal Operation mode to allow system debug.
If the Listen All Messages mode is activated, the module on the CAN bus is passive. The
transmitter buffers revert to the PORT I/O function. The receive pins remain inputs. For the
receiver, no error flags or Acknowledge signals are sent. The error counters are deactivated in
this state. The filters are disabled. Receive Buffer 0 will receive any message transferred on the
bus. This mode is useful to record all bus traffic as a bus monitor without influencing the data
traffic.
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