msm9225 Oki Semiconductor, msm9225 Datasheet - Page 7

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

Message Memory
¡ Semiconductor
1. Inside message control register (X0hex)
MMA
The message memory stores messages to be transmitted/received.
For transmission, only messages stored in the message memory can be transmitted. A message
with the highest priority among messages requested for transmission is sent.
For receiving, only messages that have an identifier stored in the message memory can be
received. When a message is received normally, and its identifier matches with the identifier
stored in the message memory, data of the received message is written to the message area of
the corresponding message in the message memory.
The message memory can store a maximum of 16 messages. Set messages at the NMES register.
0
1
This register performs various controls for a message.
Set this register for each message.
The bit configuration is as follows:
(1) Message memory access request/enable bit: MMA
¥ 0h
Address MSB
Accesses from microcontroller
to message memory are disabled
Accesses from microcontroller
to message memory are enabled
This bit prevents contention between the microcontroller and CAN when accessing the
message memory. Write "0" to the MMA bit when the microcontroller accessing ends.
Operations by the MMA bit are shown in the following table.
At reset, the MMA bit is set to "0".
message memory.
When the microcontroller accesses the message memory, "1" is written to the MMA bit
regularly. The microcontroller confirms that the MMA bit is "1", and then accesses the
Microcontroller
7
6
5
4
3
Operate
Reading of received data
Stop
Rewriting of control area
2
1
Reception
LSB
0
ARES : Automatic transmission
FRM : Message format setting
EIT : Transmission completion interrupt enable
EIR : Receive completion interrupt enable
RCS : Receive status
TRQ : Transmission request
Not used
MMA : Message memory access enable
Operate
Stop
Rewriting of control area
Rewriting of transmission data
Transmission
MSM9225
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