RM0319 datasheet(203/368 Pages) STMICROELECTRONICS

203 / 368 page

RM0319

Controller area network ports (CAN)

Doc ID 022640 Rev 3

203/368

The Mask registers (Msk28-0, UMask, MXtd, and MDir bits) may be used (UMask=’1’) to

allow groups of Data Frames with similar identifiers to be accepted. For details, see

Reception of data frame. The Dir bit should not be masked in typical applications.

15.4.12

Updating a transmit object

The CPU may update the data bytes of a transmit object any time via the IFx Interface

registers. Neither MsgVal nor TxRqst have to be reset before the update.

Even if only a part of the data bytes are to be updated, all four bytes of the corresponding

IFx Data A register or IFx Data B register have to be valid before the content of that register

is transferred to the message object. Either the CPU has to write all four bytes into the IFx

Data register or the message object is transferred to the IFx Data register before the CPU

writes the new data bytes.

When only the (eight) data bytes are updated, first 0x0087 is written to the Command Mask

To prevent the reset of TxRqst at the end of a transmission that may already be in progress

while the data is updated, NewDat has to be set together with TxRqst. For details, see

Transmission of messages.

When NewDat is set together with TxRqst, NewDat will be reset as soon as the new

transmission has started.

RM0319 Datasheet(PDF) 203 Page - STMicroelectronics