Chapter 12 Freescale’s Scalable Controller Area Network (S12MSCANV3)
MC9S12ZVM Family Reference Manual Rev. 1.3
436
Freescale Semiconductor
12.3.3.3
Data Length Register (DLR)
This register keeps the data length field of the CAN frame.
12.3.3.4
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.
Module Base + 0x00XC
7
6
5
4
3
2
1
0
R
DLC3
DLC2
DLC1
DLC0
W
Reset:
x
x
x
x
x
x
x
x
= Unused; always read “x”
Figure 12-35. Data Length Register (DLR) — Extended Identifier Mapping
Table 12-33. 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.
shows the effect of setting the DLC bits.
Table 12-34. Data Length Codes
Data Length Code
Data Byte
Count
DLC3
DLC2
DLC1
DLC0
0
0
0
0
0
0
0
0
1
1
0
0
1
0
2
0
0
1
1
3
0
1
0
0
4
0
1
0
1
5
0
1
1
0
6
0
1
1
1
7
1
0
0
0
8
