C515C_9711 Datasheet, PDF (159/268 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

On-Chip Peripheral Components
C515C
Message Configuration and Data
The following fields hold a description of the message within this object. The data field occupies the
following 8 byte positions after the message configuration register.
Note: There is no “don’t care” option for bits XTD and DIR. So incoming frames can only match with
corresponding message objects, either standard (XTD=0) or extended (XTD=1). Data
frames only match with receive-objects, remote frames only match with transmit-objects.
When the CAN controller stores a data frame, it will write all the eight data bytes into a
message object. If the data length code was less than 8, the remaining bytes of the message
object will be overwritten by non specified values.
CAN Message Configuration MCFG Register (Address XXn6H) Reset Value : UUUUUU00B
Bit No. MSB
LSB
7
6
5
4
3
2
1
0
XXn6H
DLC
rw
DIR XTD
0
rw
rw
r
0
MCFG
r
Bit
DLC
DIR
XTD
Function
Data length code
Valid values for the data length are 0...8.
Message direction
DIR=”1”: transmit. On TXRQ, the respective message object is transmitted. On
reception of a remote frame with matching identifier, the TXRQ and RMTPND bits
of this message object are set.
DIR=”0”: receive. On TXRQ, a remote frame with the identifier of this message
object is transmitted. On reception of a data frame with matching identifier, that
message is stored in this message object.
Extended identifier
Indicates, if this message object will use an extended 29-bit identifier or a standard
11-bit identifier
Semiconductor Group
6-96
1997-11-01