ST10F280_12 datasheet(167/239 Pages) STMICROELECTRONICS

167 / 239 page

ST10F280

CAN modules

Doc ID 8673 Rev. 3

167/239

Message Control Register

Address:

0xEFn0h / EEn0h XReg

Reset:

0xUUUUh

Type:

R/W

RMTPND

TXRQ

MSGLST

CPUUPD

NEWDAT

MSGVAL

TXIE

RXIE

INTPND

R/W

INTPND Interrupt Pending

Indicates, if this message object has generated an interrupt request (see TXIE and

RXIE), since this bit was last reset by the CPU, or not.

RXIE Receive Interrupt Enable

Defines, if bit INTPND is set after successful reception of a frame.

TXIE Transmit Interrupt Enable

Defines, if bit INTPND is set after successful transmission of a frame.(1)

In message object 15 (last message) these bits are hardwired to “0” (inactive) in order to prevent

transmission of message 15.

MSGVAL Message Valid

Indicates, if the corresponding message object is valid or not. The CAN controller only

operates on valid objects. Message objects can be tagged invalid, while they are

changed, or if they are not used at all.

NEWDAT New Data

Indicates, if new data has been written into the data portion of this message object by

CPU (transmit-objects) or CAN controller (receive-objects) since this bit was last

reset, or not.(2)

When the CAN controller writes new data into the message object, unused message bytes will be

overwritten by non specified values. Usually the CPU will clear this bit before working on the data, and

verify that the bit is still cleared once it has finished working to ensure that it has worked on a consistent set

of data and not part of an old message and part of the new message.

For transmit-objects the CPU will set this bit along with clearing bit CPUUPD. This will ensure that, if the

message is actually being transmitted during the time the message was being updated by the CPU, the

CAN controller will not reset bit TXRQ. In this way bit TXRQ is only reset once the actual data has been

transferred.

MSGLST

(Receive)

Message Lost (This bit applies to receive-objects only)

Indicates that the CAN controller has stored a new message into this object, while

NEWDAT was still set, i.e. the previously stored message is lost.

CPUUPD

(Transmit)

CPU Update (This bit applies to transmit-objects only)

Indicates that the corresponding message object may not be transmitted now. The

CPU sets this bit in order to inhibit the transmission of a message that is currently

updated, or to control the automatic response to remote requests.

TXRQ Transmit Request

Indicates that the transmission of this message object is requested by the CPU or via

a remote frame and is not yet done. TXRQ can be disabled by CPUUPD. (1) (3)

RMTPND Remote Pending (Used for transmit-objects)

Indicates that the transmission of this message object has been requested by a

remote node, but the data has not yet been transmitted. When RMTPND is set, the

CAN controller also sets TXRQ. RMTPND and TXRQ are cleared, when the message

object has been successfully transmitted.

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