Message Frames - Intel 8XC196K Series User Manual

Table of Contents

Table 12-5. Effect of Masking on Message Identifiers

Transmit message object ID

Mask (0 = don't care; 1 = must match) 0 0 0 0 0 0 0 0 0 1 1

Received remote message object ID

Resulting message object ID

12.3.3 Message Frames

A message object is contained within a message frame that adds control and error-detection bits

to the content of the message object. The frame for an extended message differs slightly from that

for a standard message, but they contain similar information. A data frame contains a message

object with data to be transmitted; a remote frame is a request for another node to transmit a data

frame, so it contains no data.

Figure 12-3 illustrates standard and extended message frames. Table 12-6 and Table 12-7 describe

their contents and summarize the minimum message lengths. Actual message lengths may differ

because the CAN controller adds bits during transmission (see "Error Detection and Management

Logic" on page 12-9). After each message frame, an intermission field consisting of three reces-

sive (1) bits separates messages. This intermission may be followed by a bus idle time.

Standard Frame

Extended Frame

CAN SERIAL COMMUNICATIONS CONTROLLER

Figure 12-3. CAN Message Frames

1 1 0 0 0 0 0 0 0 0 0

0 0 1 1 1 1 1 1 1 0 0