cp3cn17 National Semiconductor Corporation, cp3cn17 Datasheet - Page 90

• Manufacturer Part Number: cp3cn17
• Description: Reprogrammable Connectivity Processor With Can Interface
• Manufacturer: National Semiconductor Corporation

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15.10.3 Storage of Messages with Less Than 8 Data
The data bytes that are not used for data transfer are “don’t
cares”. If the object is transmitted, the data within these
bytes will be ignored. If the object is received, the data with-
in these bytes will be overwritten with invalid data.
SRR
IDE
RTR
ID
0E F0XCh
0E F0XEh
0E F0XAh
0E F0X8h
0E F0X6h
0E F0X4h
0E F0X2h
0E F0X0h
Address
Bytes
The Substitute Remote Request bit replaces
the RTR bit used in standard frames at this bit
position. The SRR bit needs to be set by soft-
ware if the buffer is configured to transmit a
message with an extended identifier. It will be
received as monitored on the CAN bus.
The Identifier Extension bit determines wheth-
er the message is a standard frame or an ex-
tended frame.
0 – Message is a standard frame using 11
1 – Message is an extended frame.
The Remote Transmission Request bit indi-
cates whether the message is a data frame or
a remote frame.
0 – Message is a data frame.
1 – Message is a remote frame.
The ID field is used to build the 29-bit identifier
of an extended frame.
Register
CNSTAT
Buffer
DATA0
DATA1
DATA2
DATA3
TSTP
ID0
ID1
identifier bits.
15
14
DLC
Table 42 Extended Messages with 8 Data Bytes
13
Data1[7:0]
Data3[7:0]
Data5[7:0]
Data7[7:0]
12
11
ID[28:18]
Reserved
10
90
15.10.4 Storage of Extended Messages
If the IDE bit is set, the buffer handles extended frames. The
storage of the extended ID follows the descriptions in
Table 42. The SRR bit is at the bit position of the RTR bit for
standard frame and needs to be transmitted as 1.
9
ID[14:0]
TSTP[15:0]
8
7
6
PRI
5
SRR IDE
Data2[7:0]
Data4[7:0]
Data6[7:0]
Data8[7:0]
4
3
2
ST
ID17:15]
1
RTR
0