NXP Semiconductors MC9S12G - Page 599

Scalable Controller Area Network (S12MSCANV3)
MC9S12G Family Reference Manual Rev.1.27
NXP Semiconductors 601
18.3.3.3 Data Length Register (DLR)
This register keeps the data length field of the CAN frame.
18.3.3.4 Transmit Buffer Priority Register (TBPR)
This register defines the local priority of the associated message buffer. The local priority is used for the
internal prioritization process of the MSCAN and is defined to be highest for the smallest binary number.
The MSCAN implements the following internal prioritization mechanisms:
• All transmission buffers with a cleared TXEx flag participate in the prioritization immediately
before the SOF (start of frame) is sent.
• The transmission buffer with the lowest local priority field wins the prioritization.
Module Base + 0x00XC
76543210
R
DLC3 DLC2 DLC1 DLC0
W
Reset:xxxxxxxx
= Unused; always read “x”
Figure 18-35. Data Length Register (DLR) — Extended Identifier Mapping
Table 18-34. DLR Register Field Descriptions
Field Description
3-0
DLC[3:0]
Data Length Code Bits — The data length code contains the number of bytes (data byte count) of the respective
message. During the transmission of a remote frame, the data length code is transmitted as programmed while
the number of transmitted data bytes is always 0. The data byte count ranges from 0 to 8 for a data frame.
Table 18-35 shows the effect of setting the DLC bits.
Table 18-35. Data Length Codes
Data Length Code
Data Byte
Count
DLC3 DLC2 DLC1 DLC0
00000
00011
00102
00113
01004
01015
01106
01117
10008