mc68hc05x4dw Freescale Semiconductor, Inc, mc68hc05x4dw Datasheet - Page 98

• Manufacturer Part Number: mc68hc05x4dw
• Description: Xc68hc705x4 Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Interface to the MCAN bus
Motorola CAN
MC68HC05X4
Physically, the MCAN bus may be composed of two wires. The bus can
take on one of two values: dominant or recessive. During simultaneous
transmission of dominant and recessive bits by two or more CAN
modules the resulting bus value will be dominant. (For example, with a
wired-AND implementation of the bus, the dominant level would
correspond to a logic 0, and the recessive level to a logic 1.)
The two wires of the MCAN bus are designated CANH and CANL. The
voltage levels appearing on these lines are designated V
A simple termination network is required for each wire.
the physical interface circuitry within the MCAN module, and its
connection to the MCAN bus with a typical low speed (<125 kbaud)
hardware interface. (Note that the suggested values shown in the
diagram are subject to change in the future.)
For the voltage and resistor values shown in
the MCAN bus are:
If several CAN modules are driving a dominant level on the bus at the
same time then the values for V
respectively. The residual 0.3 V is due to the voltage drop across the
diodes and driver transistors in the transmission circuit.
The receiver part of the network uses two identical voltage divider
networks, with a divide ratio of 6:1 (resistor values of 150k and 30k )
referenced to V
comparator on the physical bus lines. If the common mode range of the
comparator at its inputs is 1.5 to 3.5 volts then, for V
common mode range will be increased to –3.5 to +8.5 volts on the bus
lines.
Freescale Semiconductor, Inc.
For More Information On This Product,
– Recessive level:
– Dominant level:
Go to: www.freescale.com
DD
/2. This increases the common mode range of the input
Motorola CAN
V
V
CANH
CANH
CANH
= 3.25 V
= 1.00 V
and V
CANL
Figure 21
can go to 0.3 and 4.7 volts
V
V
CANL
CANL
DD
= 1.75 V
= 4.00 V
Figure 21
= 5.0 V, the
the voltages on
CANH
and V
shows
30-mcan
CANL
.