msm9225 Oki Semiconductor, msm9225 Datasheet - Page 37

• Manufacturer Part Number: msm9225
• Description: Can Controller Area Network Controller
• Manufacturer: Oki Semiconductor

Operation at Receiving Message
1. Priority of message
2. Data length code
3. Group message function
¡ Semiconductor
A message has the priority determined by the identifier setting. To determine priority,
identifiers of messages are compared from the higher bit, and the identifier (set to "0") detected
first has the higher priority. (see the example below)
When the received data length code (hereafter DLC) matches the DLC being set to the message
memory, the number of bytes of data indicated by the received DLC is received and written to
the message memory. When the received DLC does not match with the DLC being set to
message memory, the MSM9225 operates as follows:
If the group message function is used, a part of an identifier can be masked. This can increase
the number of receivable identifiers.
To use the group message function, set the message number of the target message to set the
group message function at the GMR register. Then set the bits to be masked at the GMSK
register. Depending on the location of bits to be masked, an another identifier being set at the
message memory may be received.
In this case, the priority of identifiers being set on the message memory is calculated and the
identifier having the highest priority is received. The received data is written to the message
memory indicated by the message for which the identifier with the highest priority is set.
(1) Received DLC > DLC on message memory
(2) DLC on message memory > received DLC
0
0
1
0
Identifier (example)
The number of bytes of data indicated by the DLC on the message memory is received
and written to the message memory.
The data exceeding the number of bytes indicated by DLC on the memory is not written
to message memory.
The number of bytes of data indicated by the received DLC is received and written to the
message memory.
0
0
0
0
0
0
0
1
0
0
0
0
1
1
0
0
1
0
0
1
1
1
0
0
0
0
0
1
In this example, priority is determined at the shaded bits.
1
1
1
1
0
0
0
0
1
1
1
1
Priority
Second
First
Fourth
Third
MSM9225
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