RM0319 datasheet(195/368 Pages) STMICROELECTRONICS

195 / 368 page

RM0319

Controller area network ports (CAN)

Doc ID 022640 Rev 3

195/368

Figure 67.

Data transfer between IFx registers and message RAM

After the partial write of a message object, that Message Buffer registers that are not

selected in the Command Mask register will set to the actual contents of the selected

message object.

After the partial read of a message object, those Message Buffer registers that are not

selected in the Command Mask register will be left unchanged.

Transmission of messages

If the shift register of the CAN core cell is ready for loading and there is no data transfer

between the IFx registers and the message RAM, the MsgVal bits in the Message Valid

message object with the highest priority pending transmission request is loaded into the

Shift register by the message handler and the transmission is started. The message object

NewDat bit is reset.

After a successful transmission and if no new data has been written to the message object

(NewDat = ‘0’) since the start of the transmission, the TxRqst bit resets. If TxIE is set, IntPnd

Start

Write Command Request Register

Busy = 1

CAN_WAIT_B = 0

WR/RD = 1

Read Message Object to IFx

Write IFx to Message RAM

Read Message Object to IFx

Busy = 0

CAN_WAIT_B = 1

Yes

RM0319 Datasheet(PDF) 195 Page - STMicroelectronics