STM8S datasheet(385/467 Pages) STMICROELECTRONICS

385 / 467 page

DocID14587 Rev 14

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RM0016

Controller area network (beCAN)

427

By transmit request order:

The transmit mailboxes can be configured as a transmit FIFO by setting the TXFP bit in the

CAN_MCR register. In this mode the priority order is given by the transmit request order.

This mode is very useful for segmented transmission.

Abort

A transmission request can be aborted by the user setting the ABRQ bit in the CAN_MCSR

request while the mailbox is in transmit state can have two results. If the mailbox is

transmitted successfully the mailbox becomes empty with the TXOK bit set in the

CAN_MCSR and CAN_TSR registers. If the transmission fails, the mailbox becomes

scheduled, the transmission is aborted and becomes empty with TXOK cleared. In all

cases the mailbox will become empty again at least at the end of the current transmission.

Non-automatic retransmission mode

This mode has been implemented in order to fulfil the requirement of the Time Triggered

Communication option of the CAN standard. To configure the hardware in this mode the

NART bit in the CAN_MCR register must be set.

In this mode, each transmission is started only once. If the first attempt fails, due to an

arbitration loss or an error, the hardware will not automatically restart the message

transmission.

At the end of the first transmission attempt, the hardware considers the request as

completed and sets the RQCP bit in the CAN_MCSR register. The result of the transmission

is indicated in the CAN_MCSR register by the TXOK, ALST and TERR bits.

STM8S データシート(PDF) 385 Page - STMicroelectronics