Datasheet

MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
Freescale Semiconductor 335
Chapter 27
Byte Data Link Controller (BDLC)
27.1 Introduction
The byte data link controller (BDLC) provides access to an external serial communication multiplex bus,
operating according to the Society of Automotive Engineers (SAE) J1850 protocol.
The BDLC-D is only available on the MC68HC908AS60A.
27.2 Features
Features of the BDLC module include:
• SAE J1850 class B data communications network interface compatible and ISO compatible for low
speed (<
125 kbps) serial data communications in automotive applications
• 10.4 kbps variable pulse width (VPW) bit format
• Digital noise filter
• Collision detection
• Hardware cyclical redundancy check (CRC) generation and checking
• Two power-saving modes with automatic wakeup on network activity
• Polling and CPU interrupts available
• Block mode receive and transmit supported
• Supports 4X receive mode, 41.6 kbps
• Digital loopback mode
• Analog loopback mode
• In-frame response (IFR) types 0, 1, 2, and 3 supported
27.3 Functional Description
Figure 27-1 shows the organization of the BDLC module. The CPU interface contains the software
addressable registers and provides the link between the CPU and the buffers. The buffers provide storage
for data received and data to be transmitted onto the J1850 bus. The protocol handler is responsible for
the encoding and decoding of data bits and special message symbols during transmission and reception.
The MUX interface provides the link between the BDLC digital section and the analog physical interface.
The wave shaping, driving, and digitizing of data is performed by the physical interface.
Use of the BDLC module in message networking fully implements the SAE Standard J1850 Class B Data
Communication Network Interface specification.
NOTE
It is recommended that the reader be familiar with the SAE J1850 document
and ISO Serial Communication document prior to proceeding with this
chapter of the specification.