50.9.21 CAN Message Control Register
| Name: | CAN_MCRx |
| Offset: | 0x021C + x*0x20 [x=0..7] |
| Reset: | 0x00000000 |
| Property: | Read/Write |
| Bit | 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | |
| Access | |||||||||
| Reset |
| Bit | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | |
| MTCR | MACR | MRTR | MDLC[3:0] | ||||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | ||
| Reset | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ||
| Bit | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | |
| Access | |||||||||
| Reset |
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
| Access | |||||||||
| Reset |
Bit 23 – MTCR Mailbox Transfer Command
This flag clears the MRDY and MABT flags in CAN_MSRx.
When several mailboxes are requested to be transmitted simultaneously, they are transmitted in turn. The mailbox with the highest priority is serviced first. If several mailboxes have the same priority, the mailbox with the lowest number is serviced first (i.e., MBx0 will be serviced before MBx 15 if they have the same priority).
It is possible to set MTCR for several mailboxes at the same time by writing to CAN_TCR.
| Mailbox Object Type | Description |
| Receive | Allows the reception of the next message |
| Receive with Overwrite | Triggers a new reception |
| Transmit | Sends data prepared in the mailbox as soon as possible |
| Consumer | Sends a remote transmission frame |
| Producer | Sends data prepared in the mailbox after receiving a remote frame from a Consumer |
Bit 22 – MACR Abort Request for Mailbox x
This flag clears the MRDY and MABT flags in CAN_MSRx.
It is possible to set the MACR field for several mailboxes at the same time, setting several bits to CAN_ACR.
| Mailbox Object Type | Description |
| Receive | No action |
| Receive with Overwrite | No action |
| Transmit | Cancels transfer request if the message has not been transmitted to the CAN transceiver |
| Consumer | Cancels the current transfer before the remote frame has been sent |
| Producer | Cancels the current transfer. The next remote frame will not be serviced |
Bit 20 – MRTR Mailbox Remote Transmission Request
Consumer situations can be handled automatically by setting the mailbox object type in Consumer. This requires only one mailbox.
It can also be handled using two mailboxes, one in reception, the other in transmission. The MRTR and the MTCR bits must be set at the same time.
| Mailbox Object Type | Description |
| Receive | No action |
| Receive with Overwrite | No action |
| Transmit | Sets the RTR bit in the sent frame |
| Consumer | No action, the RTR bit in the sent frame is set automatically |
| Producer | No action |
Bits 19:16 – MDLC[3:0] Mailbox Data Length Code
| Mailbox Object Type | Description |
| Receive | No action |
| Receive with Overwrite | No action |
| Transmit | Length of the mailbox message |
| Consumer | No action |
| Producer | Length of the mailbox message to be sent after the remote frame reception |