MC68HC912BD32 Datasheet, PDF (175/292 Pages) Freescale Semiconductor, Inc – Advance Information

Freescale Semiconductor, Inc.
Byteflight™ Module
Byteflight™ Protocol
Byteflight™ Protocol
Byteflight™ Format The BMW Byteflight™ protocol defines the message format, as follows:
and Timing
# BYTES: 1
1
IDLE
ID
LEN
0...12
DATAn
1
1
CRCH CRCL
IDLE
Figure 26 Byteflight™ Message Format
The identifier (ID) byte is followed by the length (LEN) byte, which
contains the number of data bytes (0..12) of the message. Following the
data bytes (DATAn) are two CRC bytes (CRCH,CRCL), which contain
the checksum. The value zero is not allowed for any identifier (ID). The
priority of an identifier is inversely proportional to its value.
START MSB
ONE BYTE FRAME
t_bit
LSB STOP
Figure 27 Byteflight™ Byte Format
One byte of a message is embedded into a start bit (‘1’) and a stop bit
(‘0’), which are synchronization symbols and distinguish a message from
a SYNC pulse. The transfer starts with the MSB first. The dominant state
is represented by a logical ‘0’ and the recessive state is represented by
a logical ‘1’.
IDLE
MESSAGE START
SEQUENCE
ONE BYTE FRAME
START MSB
LSB STOP
Figure 28 Byteflight™ Message Start Sequence
5-sibus
Byteflight™ Module
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MC68HC912BD32 Rev 1.0