MC912DG128A Motorola, MC912DG128A Datasheet - Page 273

• Manufacturer Part Number: MC912DG128A
• Description: Microcontrollers
• Manufacturer: Motorola

5-mscan12
MOTOROLA
NOTE:
content of RxBG into RxFG
interrupt to the CPU
after the IFS field of the CAN frame) will be received into RxBG. The
over-writing of the background buffer is independent of the identifier filter
function.
The user’s receive handler has to read the received message from
RxFG and to reset the RXF flag in order to acknowledge the interrupt
and to release the foreground buffer.
An overrun condition occurs when both the foreground and the
background receive message buffers are filled with correctly received
messages with accepted identifiers and a further correctly received
message with accepted identifier is received from the bus. The latter
message will be discarded and an error interrupt with overrun indication
will occur if enabled. As long as both buffers remain filled, the msCAN12
is able to transmit messages but it will discard all incoming messages.
The msCAN12 will receive its own messages into the background
receive buffer RxBG but will not overwrite RxFG and will not emit a
receive interrupt nor will it acknowledge (ACK) its own messages on the
CAN bus. The exception to this rule is that when in loop-back mode
msCAN12 will treat its own messages exactly like all other incoming
messages.
1. Only if the RXF flag is not set.
2. The receive interrupt will occur only if not masked. A polling scheme can be applied on RXF
also.
MSCAN Controller
2
. A new message (which may follow immediately
1
, sets the RXF flag, and emits a receive
MC68HC912DT128A Rev 2.0
MSCAN Controller
Message Storage
273