mc68hc908as60 Freescale Semiconductor, Inc, mc68hc908as60 Datasheet - Page 337

• Manufacturer Part Number: mc68hc908as60
• Description: Mc68hc908as60 Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

21.5.2 J1850 Frame Format
21.5.2.1 Start-of-Frame Symbol (SOF)
MC68HC908AS60 — Rev. 1.0
For example, if the frequency of the MUX interface clock (f
1.0486 MHz, then the period (t
delay in the absence of noise will be 15.259 s.
The effect of random noise on the BDRxD signal depends on the
characteristics of the noise itself. Narrow noise pulses on the BDRxD
signal will be ignored completely if they are shorter than the filter delay.
This provides a degree of low pass filtering.
If noise occurs during a symbol transition, the detection of that transition
can be delayed by an amount equal to the length of the noise burst. This
is just a reflection of the uncertainty of where the transition is truly
occurring within the noise.
Noise pulses that are wider than the filter delay, but narrower than the
shortest allowable symbol length, will be detected by the next stage of
the BDLC’s receiver as an invalid symbol.
Noise pulses that are longer than the shortest allowable symbol length
will be detected normally as an invalid symbol or as invalid data when
the frame’s CRC is checked.
All messages transmitted on the J1850 bus are structured using the
format shown in
J1850 states that each message has a maximum length of 101 PWM bit
times or 12 VPW bytes, excluding SOF, EOD, NB, and EOF, with each
byte transmitted most significant bit (MSB) first.
All VPW symbol lengths described here are typical values at a 10.4-kbps
bit rate.
All messages transmitted onto the J1850 bus must begin with a
long-active 200- s period SOF symbol. This indicates the start of a new
message transmission. The SOF symbol is not used in the CRC
calculation.
Freescale Semiconductor, Inc.
For More Information On This Product,
Byte Data Link Controller-Digital (BDLC-D)
Go to: www.freescale.com
Figure
21-6.
BDLC
) is 954 ns and the maximum filter
Byte Data Link Controller-Digital (BDLC-D)
BDLC MUX Interface
BDLC
Technical Data
) is