MC68HC58 Motorola, MC68HC58 Datasheet - Page 35

• Manufacturer Part Number: MC68HC58
• Description: Data Link Controller
• Manufacturer: Motorola

3.1 J1850 Frame Format
MC68HC58
TECHNICAL DATA
IDLE
This section explains the frame format used to transmit and receive information on the
J1850 bus. Variable pulse width modulation (VPW) valid/invalid bits and symbols are
also discussed.
A J1850 bus message consists of one or more frames. Each frame is composed of
multiple symbols. Refer to Figure 3-1.
A symbol starts with a transition from either an active to a passive level, or a passive
to an active level. Symbols end with another transition, or the absence of a transition
after a specified time period. Figure 3-2 illustrates the representative symbols for a
J1850 message frame.
SOF
DATA
0
Figure 3-1 J1850 Bus Message Components
Figure 3-2 J1850 Bus Frame Format (VPW)
SECTION 3 J1850 FRAME FORMAT
DATA
SYMBOLS
FRAME
1
J1850 FRAME FORMAT
DATA
MESSAGE
SYMBOLS
FRAME
N
CRC
SYMBOLS
FRAME
E
O
D
NB
OPTIONAL
IFR
EOF
J1850 BUS FRAME FORMAT
J1850 BUS MESS COMP
MOTOROLA
F
S
I
IDLE
3-1