MC68HC08GZ32 Datasheet, PDF (132/320 Pages) Freescale Semiconductor, Inc – Microcontrollers

MSCAN08 Controller (MSCAN08)
12.12.2 Identifier Registers
The identifiers consist of either 11 bits (ID10–ID0) for the standard, or 29 bits (ID28–ID0) for the extended
format. ID10/28 is the most significant bit and is transmitted first on the bus during the arbitration
procedure. The priority of an identifier is defined to be highest for the smallest binary number.
SRR — Substitute Remote Request
This fixed recessive bit is used only in extended format. It must be set to 1 by the user for transmission
buffers and will be stored as received on the CAN bus for receive buffers.
IDE — ID Extended
This flag indicates whether the extended or standard identifier format is applied in this buffer. In case
of a receive buffer, the flag is set as being received and indicates to the CPU how to process the buffer
identifier registers. In case of a transmit buffer, the flag indicates to the MSCAN08 what type of
identifier to send.
1 = Extended format, 29 bits
0 = Standard format, 11 bits
RTR — Remote Transmission Request
This flag reflects the status of the remote transmission request bit in the CAN frame. In case of a
receive buffer, it indicates the status of the received frame and supports the transmission of an
answering frame in software. In case of a transmit buffer, this flag defines the setting of the RTR bit to
be sent.
1 = Remote frame
0 = Data frame
12.12.3 Data Length Register (DLR)
This register keeps the data length field of the CAN frame.
DLC3–DLC0 — Data Length Code Bits
The data length code contains the number of bytes (data byte count) of the respective message. At
transmission of a remote frame, the data length code is transmitted as programmed while the number
of transmitted bytes is always 0. The data byte count ranges from 0 to 8 for a data frame. Table 12-5
shows the effect of setting the DLC bits.
Table 12-5. Data Length Codes
DLC3
0
0
0
0
0
0
0
0
1
Data Length Code
DLC2 DLC1
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
0
0
DLC0
0
1
0
1
0
1
0
1
0
Data Byte
Count
0
1
2
3
4
5
6
7
8
MC68HC08GZ32 Data Sheet, Rev. 3
132
Freescale Semiconductor