AN1212 Freescale Semiconductor / Motorola, AN1212 Datasheet - Page 10

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

AN1212/D
Host Interface
10
J1850 Multiplex Bus Communication Using the MC68HC705C8
and the SC371016 J1850 Communications Interface (JCI)
The JCI has three different serial host interface modes which can be used to
interface the JCI to a wide variety of microcontrollers.These three interface
modes include:
These three interface modes provide the host MCU with a choice of two eight-
conductor or one five-conductor, high speed, synchronous serial interfaces to
the JCI.
The handshake SPI mode is an eight-conductor, full-handshake synchronous
serial interface. This mode has three conductors for data transfer, and five for
data control and error indication. The three conductor data transfer is
compatible with the Motorola serial peripheral interface, preforming an 8-bit
"data exchange" between the host MCU and the JCI during each byte transfer.
The five control lines are used to delineate data transfers between the host
MCU and the JCI, inform the host MCU when the JCI has received a message
from the MUX bus, and to indicate to the host when a transmission error has
been detected.
The handshake SCI mode is also an eight-conductor, full-handshake
synchronous serial interface, having three conductors for data transfer and five
for data control and error indication. The three-conductor data transfer is similar
in format to the Motorola serial communications interface, although the host
MCU must also supply a serial clock to the JCI.
The enhanced SPI mode is a five-conductor synchronous serial interface,
compatible with the Motorola serial peripheral interface (SPI). Data is
transferred between the host MCU and the JCI in pairs of 8-bit SPI transfers.
During the first transfer of each pair, the host MCU transmits a byte of data,
which may or may not be valid, to the JCI, while the JCI transmits a status byte
to the host MCU, in which is encoded the current status of the JCI. During the
second transfer of each pair, the host MCU transmits a command byte to the
JCI which can contain a variety of transmit, receive, or general commands,
while the JCI transfers a data byte to the host MCU, which may or may not be
valid.
For more information on each of these host interface modes, refer to the J1850
Communications Interface Specification, Chapter 4: MCU Interface.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Handshake SPI mode
Handshake SCI mode
Enhanced SPI mode
Go to: www.freescale.com
MOTOROLA