Datasheet
Table Of Contents
- List of Sections
- Table of Contents
- General Description
- Central Processing Unit (CPU)
- Pinout and Signal Description
- System Configuration
- Registers
- Operating Modes
- Resource Mapping
- Bus Control and Input/Output
- Resets and Interrupts
- Voltage Regulator (VREG)
- Flash EEPROM 256K
- EEPROM 4K
- Port Integration Module
- Clocks and Reset Generator (CRG)
- Pulse Width Modulator (PWM)
- Enhanced Capture Timer (ECT)
- Serial Communications Interface (SCI)
- Serial Peripheral Interface (SPI)
- Inter-IC Bus (IIC)
- MSCAN
- Analog to Digital Converter
- Byte Data Link Controller Module
- Contents
- Overview
- Features
- Block Diagram
- Register Map
- Functional Description
- Register Descriptions
- External Pin Descriptions
- Reset Initialization/Basic Operation
- Transmitting A Message
- Receiving A Message
- Transmitting An In-Frame Response (IFR)
- Receiving An In-Frame Response (IFR)
- Special BDLC Operations
- Modes of Operation
- Interrupt Operation
- Low Power Options
- Background Debug Module (BDM)
- Breakpoint (BKP) Module
- Revision History
- Glossary
- Literature Updates

Byte Data Link Controller Module
Transmitting A Message
MC9S12DP256 — Revision 1.1
Byte Data Link Controller Module
DLCBDR by the CPU. For an illustration of the DLCBDR, refer to BDLC
Data Register (DLCBDR).
Transmitting a
Message with the
BDLC
To transmit a message using the BDLC, the user just writes the first byte
of the message to be transmitted into the DLCBDR, initiating the
transmission process. When the TDRE status appears in the DLCBSVR,
the user writes the next byte into the DLCBDR. Once all of the bytes
have been loaded into the DLCBDR, the user sets the TEOD bit, and the
BDLC completes the message transmission. What follows is an
overview of the basic steps required to transmit a message onto an SAE
J1850 network using the BDLC. For an illustration of this sequence, refer
to Basic BDLC Transmit Flowchart.
NOTE:
Due to the byte-level architecture of the BDLC module, the 12-byte limit
on message length as defined in SAE J1850 must be enforced by the
user’s software. The number of bytes in a message (transmitted or
received) has no meaning to the BDLC.
Step 1: Write the
First Byte into the
DLCBDR
To initiate a message transmission, the CPU simply loads the first byte
of the message to be transmitted into the DLCBDR. The BDLC will then
perform the necessary bus acquisition duties to determine when the
message transmission can begin.
Once the BDLC determines that the SAE J1850 bus is free, a Start of
Frame (SOF) symbol will be transmitted, followed by the byte written to
the DLCBDR. Once the BDLC readies this byte for transmission, the
DLCBSVR will reflect that the next byte can be written to the DLCBDR
(TDRE interrupt).
NOTE:
If the user writes the first byte of a message to be transmitted to the
DLCBDR and then determines that a different message should be
transmitted, the user can write a new byte to the DLCBDR up until the
transmission begins. This new byte will replace the original byte in the
DLCBDR.
Freescale Semiconductor, I
Freescale Semiconductor, Inc.
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