SAE 81C90/91
07Feb95@09:05h Intermediate Version
Descriptor Registers
A descriptor register is available for each message object and contains the eleven bits of the
message identifier (ID.0 through ID.10), the remote-transmission-request bit (RTR) and the data
length code (DLC) of a message.
DRnH
7
6
5
4
3
2
1
0
Address: XX
ID.10
rw
ID.9
rw
ID.8
rw
ID.7
rw
ID.6
rw
ID.5
rw
ID.4
rw
ID.3
rw
H
Reset Value: UU
H
DRnL
7
6
5
4
3
2
1
0
Address: XX
ID.2
rw
ID.1
rw
ID.0
rw
RTR
rw
DLC
H
Reset Value: UU
rw
rw
rw
rw
H
Bit(field)
DLC
Function
Data Length Code
Defines the number of data bytes of message n.
Defined values are 0000...1000, i.e. 0...8 bytes. Other values are not permitted.
RTR
Remote Transmission Request Bit
‘0’: This message operates as a data frame.
‘1’: This message operates as a remote frame.
Note: See description and table below.
ID.10-0
n = 0...15
Identifier
Identifier associated with message n, controls the acceptance of received frames
and is inserted into transmitted frames.
Bit RTR determines the function of the corresponding message object when it is transmitted, and its
reaction on a received data frame or remote frame.
The table below summarizes the message object’s behaviour in the different cases.
RTR bit Object is transmitted
Matching Data Frame
received
Matching Remote Frame
received
’0’
The message object is
The data frame is stored in The remote frame is
(data
transmitted as a standard
the message object.
ignored.
frame) data frame.
’1’
The message object is
The data frame is ignored
and not stored.
The message object is sent
as a data frame.
(remote transmitted as a remote
frame) frame (i.e. a request).
Note: For the transmission of remote frames (RTR = 1) the data-length-code should be set to ‘0’.
Semiconductor Group
13
INFINEON [ Infineon ]
