National CP3BT26 - Manual (Page 131)

131 www.national.com
CP3
BT26
19.10.3 Storage of Messages with Less Than 8 Data
Bytes
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.
19.10.4 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 55. The SRR bit is at the bit position of the RTR bit for
standard frame and needs to be transmitted as 1.
SRR 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.
IDE 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
identifier bits.
1 – Message is an extended frame.
RTR 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.
ID The ID field is used to build the 29-bit identifier
of an extended frame.
Table 55 Extended Messages with 8 Data Bytes
Address
Buffer
Register
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0E F0XEh ID1 ID[28:18] SRR IDE ID17:15]
0E F0XCh ID0 ID[14:0] RTR
0E F0XAh DATA0 Data1[7:0] Data2[7:0]
0E F0X8h DATA1 Data3[7:0] Data4[7:0]
0E F0X6h DATA2 Data5[7:0] Data6[7:0]
0E F0X4h DATA3 Data7[7:0] Data8[7:0]
0E F0X2h TSTP TSTP[15:0]
0E F0X0h CNSTAT DLC Reserved PRI ST