AN1212 Freescale Semiconductor / Motorola, AN1212 Datasheet - Page 11

• Manufacturer Part Number: AN1212
• Description: J1850 Multiplex Bus Communication Using the MC68HC705C8 and the SC371016 J1850 Communications Interface (JCI)
• Manufacturer: Freescale Semiconductor / Motorola

JCI Control/
Configuration Inputs
MOTOROLA
J1850 Multiplex Bus Communication Using the MC68HC705C8
and the SC371016 J1850 Communications Interface (JCI)
The JCI has 12 inputs that are used to determine:
These inputs are normally tied to either a logic 1 or logic 0 in the application,
though each can be connected to a host MCU I/O port pin for greater flexibility.
The mode select pins (MODE1:0) are used to determine which interface mode
the JCI will use to communicate with the host MCU. Because these pins are
level sensitive, the user must take care not to inadvertently change the logic
level on one of these inputs, as communication with the JCI will be disrupted.
Table 2
The COMSEL input is used in conjunction with the input oscillator frequency to
determine which modulation technique and bit rate the JCI will use to transmit
and receive frames on the MUX bus. COMSEL is normally tied to a logic 1 or
logic 0 in the application, but it can be connected to a host I/O pin which can be
used to control both the logic level of the COMSEL input and an input oscillator
control circuit, allowing the user to switch between modulation techniques and
transmission bit rates.
determined by the logic level of the COMSEL input and the input oscillator
frequency.
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Freescale Semiconductor, Inc.
For More Information On This Product,
8 MHz
8 MHz
4 MHz
4 MHz
The host interface mode
The message transmission rate
Modulation technique
Whether an in-frame response is required
The physical address of the node
f
osc
shows the interface mode selection criteria for the mode inputs.
Table 3. Communication Rate and Format Selection
MODE0
V
V
V
V
DD
DD
SS
SS
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COMSEL
Table 2. JCI Interface Mode Selection
V
V
V
V
DD
DD
SS
SS
Table 3
MODE1
V
V
V
V
SS
DD
SS
DD
shows the modulation and bit rate selections as
Communication
Baud Rates
41.7 kbps
20.8 kbps
20.8 kbps
10.4 kbps
Test mode enable
Operating Mode
Handshake SCI
Handshake SPI
Enhanced SPI
Communication
Format
PWM
PWM
VPW
VPW
JCI OVERVIEW
AN1212/D
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