cp3cn17 National Semiconductor Corporation, cp3cn17 Datasheet - Page 89

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

PRI
DLC
0E F0XCh
0E F0XEh
0E F0XAh
0E F0X8h
0E F0X6h
0E F0X4h
0E F0X2h
0E F0X0h
Address
The Transmit Priority Code field holds the
software-defined transmit priority code for the
message buffer.
The Data Length Code field determines the
number of data bytes within a received/trans-
mitted frame. For transmission, these bits
need to be set according to the number of
data bytes to be transmitted. For reception,
these bits indicate the number of valid re-
ceived data bytes available in the message
buffer. Table 40 shows the possible bit combi-
nations for DLC3:0 for data lengths from 0 to
8 bytes.
Register
CNSTAT
Buffer
DATA0
DATA1
DATA2
DATA3
TSTP
ID1
ID0
Table 40 Data Length Coding
0000
0001
0010
0011
0100
0101
0110
0111
1000
DLC
15
14
DLC
Number of Data Bytes
Table 41 Standard Frame with 8 Data Bytes
13
Data1[7:0]
Data3[7:0]
Data5[7:0]
Data7[7:0]
12
0
1
2
3
4
5
6
7
8
11
ID[10:0]
Reserved
10
89
Note: The maximum number of data bytes received/trans-
mitted is 8, even if the DLC field is set to a value greater than
8. Therefore, if the data length code is greater or equal to
eight bytes, the DLC field is ignored.
15.10.2 Storage of Standard Messages
During the processing of standard frames, the Extended-
Identifier (IDE) bit is clear. The ID1[3:0] and ID0[15:0] bits
are “don’t care” bits. A standard frame with eight data bytes
is shown in Table 41.
IDE
RTR
ID
9
TSTP[15:0]
Don’t Care
8
7
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 for the 11 standard frame
identifier bits.
identifier bits.
6
PRI
5
RTR IDE
Data2[7:0]
Data4[7:0]
Data6[7:0]
Data8[7:0]
4
3
www.national.com
2
Don’t Care
ST
1
0