305
μPD780948, μPD78F0948, μPD780949, μPD78F0949
WAKE
Wakeup Condition
0
Normal operation
1
Sleep mode has been cancelled
OVER
Overrun Condition
0
Normal operation
1
Overrun occured during access to RAM
Overrun Situation
Cannot get transmit data.
When detected
DCAN Behavior
Next data byte request from
protocol.
Immediate during the frame.
The frame itself conforms to the
CAN specification, but its content
is faulty.
Corrupted data or ID in the
e.
TXRQ1/0 is not cleared. DCAN
will retransmit the correct frame
after synchronization to the bus.
Data in RAM is inconsistent. No
receive flags. DN and MUC bit
may be set in message.
Message is not received and its
data is lost.
Cannot store receive data.
Data storage is ongoing during
the six bit of the next frame.
Cannot get data for ID
comparison
ID compare is ongoing during six
bits of next frame.
This bit is set and an error interrupt is generated under the following circumstances:
a) A CAN bus activities occurs during SLEEP condition of CAN protocol.
b) Any try to set sleep mode in CAN control register during receive or transmit operation will immediately
set the Wake up condition.
The CPU must clear this bit after recognition, because the error interrupt line is kept active as long as
this bit is set.
Cautions:
1. The WAKE bit is cleared to “0” if CPU writes “1” to it, or when the INIT-bit in CANC
is set.
2. Writing a 0 to the WAKE bit has no influence.
The Overrun condition is set whenever the CAN can not make all RAM accesses that are necessary for
sorting and storing receive data or fetching transmit data. An error interrupt is generated at the same time.
An overrun condition will
not
occur under the following circumstances:
The DCAN clock as defined with the PRM bits in the BRPRS register is at minimum 16 times of the CAN
baudrate
and
the selected CPU clock (defined in the DCC register) is at minimum 8 times of the baudrate.
Possible reasons are:
Too many messages are defined.
DMA access to RAM area is too slow compared to the CAN Baudrate.
The possible reactions of the DCAN differ depending on the situation, when the overrun occurs.
Table 18-26: Possible Reactions of the DCAN