MSM9225 データシートの表示（PDF） - Oki Electric Industry

部品番号

コンポーネント説明

メーカー

MSM9225

CAN (Controller Area Network) Controller

Oki Electric Industry 

¡ Semiconductor

MSM9225

Message Memory

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.

1. Inside message control register (X0hex)

This register performs various controls for a message.

Set this register for each message.

The bit configuration is as follows:

Address MSB

LSB

¥ 0h

76543210

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

(1) Message memory access request/enable bit: MMA

This bit prevents contention between the microcontroller and CAN when accessing the

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

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".

MMA

Microcontroller

Accesses from microcontroller

0

to message memory are disabled

Reception

Operate

Reading of received data

Accesses from microcontroller Stop

1

to message memory are enabled Rewriting of control area

Transmission

Operate

Stop

Rewriting of control area

Rewriting of transmission data

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