Fujitsu FR81S User Manual

CHAPTER 41: CAN

4. Registers

FUJITSU SEMICONDUCTOR LIMITED

CHAPTER

: CAN

FUJITSU SEMICONDUCTOR CONFIDENTIAL

[bit5]: Automatic retransmission disable bit

The CAN controller retransmits the frame automatically when it loses the arbitration or when an error is

detected during transfer. To enable automatic retransmission, set "0" to the DAR bit. In order to operate

CAN in Time Triggered CAN environments, "1" needs to be set to the DAR bit.

DAR

Function

Enables the automatic retransmission of the message when CAN loses the arbitration or

when an error is detected. [Initial value]

Disables automatic retransmission.

Notes:

When "1" is set to the DAR bit, the values for the TxRqst and NewDat bits of the message objects are as

follows: (For message objects, see "4.4 Message Object".)

⋅

When frame transmission is started, the TxRqst bit for the message object is cleared to "0", but the

NewDat bit remains to be "1".

⋅

When frame transmission is completed successfully, the NewDat bit is cleared to "0".

When the transmission loses the arbitration or when an error is detected, the NewDat bit remains to be

set to "1". To restart the transmission, set "1" to the TxRqst bit.

⋅

When the DAR bit in the CAN control register (CTRLR) is changed from "0" to "1" during frame

transmission (TxRqst=1), the frame that is being sent is retried. Thus, change the DAR bit only when

the Init bit is "1".

⋅

The transmission operations when "1" is set to the DAR bit and several message buffers are used are

as follows:

⋅

When "1" is set to TxRqst of *other* message buffers (when "1" is set to TxRqst of several message

buffers) before CAN starts frame transmission or during transmission, all TxRqst set are reset to "0"

and the data of the highest order message buffer is sent when frame transmission is started.

⋅

When frame transmission is completed successfully, NewDat of sent message buffer is reset to "0",

and IntPnd of the message object is set to "1" when the TxIE of the message buffer is "1".

⋅

Other message buffers do not send frames at frame transmission start because TxRqst is reset to "0".

After the message buffer sent by NewDat or IntPnd is checked, "1" needs to be set to TxRqst and

NewDat again for the message buffer to be sent.

[bit4] Reserved bit

The read value is always "0". When writing to this bit, set "0".

[bit3]: Error interrupt code enable bit

EIE

Function

Disables the interrupt code setting to the CAN interrupt register (INTR) with the bit

change for Boff or EWarn of the CAN status register (STATR). [Initial value]

Enables the status interrupt code setting to the CAN interrupt register (INTR) with the

bit change for Boff or EWarn of the CAN status register (STATR).

MB91520 Series

MN705-00010-1v0-E

1710