Specifying A Message Object's Configuration - Intel 8XC196K Series User Manual

12.5.1 Specifying a Message Object's Configuration

Each message object configuration register (Figure 12-12) specifies a message identifier type
(standard or extended), transfer direction (transmit or receive), and data length (in bytes).
CAN_MSG x CFG
x = 1–15 (87C196CA)
Program the CAN message object x configuration (CAN_MSG x CFG) register to specify a message
object's data length, transfer direction, and identifier type.
7
87C196CA DLC3
Bit Bit
Number Mnemonic
7:4 DLC3:0
3 DIR
2 XTD
1:0 —
Figure 12-12. CAN Message Object x Configuration (CAN_MSGxCFG) Register
Set the XTD bit for a message object with an extended identifier; clear it for a message with a
standard identifier. If you accidentally clear the XTD bit for a message that has an extended iden-
tifier, the CAN controller will clear the extended bits in the identification register. If you set the
XTD bit for a message object, that message object cannot receive message objects with standard
identifiers.
For a transmit message, set the DIR bit and write the number of programmed data bytes (0–8) to
the DLC field. For a receive message, clear the DIR bit. The CAN controller stores the data length
from the received message in the DLC field.
CAN SERIAL COMMUNICATIONS CONTROLLER
DLC2 DLC1 DLC0
Data Length Code
Specify the number of data bytes this message object contains. Valid
values are 0–8. The CAN controller updates a receive message object's
data length code after each reception to reflect the number of data bytes in
the current message.
Direction
Specify whether this message object is to be transmitted or is to receive a
message object from a remote node.
0 = receive
1 = transmit
Extended Identifier Used
Specify whether this message object's identification registers contain an
extended (29-bit) or a standard (11-bit) identifier.
0 = standard identifier
1 = extended identifier
Reserved; for compatibility with future devices, write zeros to these bits.
Address: 1E x 6H ( x = 1–F)
Reset State: Unchanged
DIR XTD
Function
0
— —
12-21