Distributor of Microchip Technology: Excellent Integrated System Limited
Datasheet of TDGL004 - BOARD CEREBOT 32MX7 PIC32MX795
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Cerebot 32MX7 Reference Manual
www.digilentinc.com
page 7 of 19
Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.
The PIC32MX795 microcontroller provides two
sets of pins that can be used to connect the
CAN controllers to the external transceivers.
The Cerebot 32MX7 is designed to use the
alternate (not the standard) pins. This selection
is made using the configuration variables in the
microcontroller, set using a
#pragma config
statement. To select the use of the alternate
interface pins, the following statement must
appear in the main program module:
#pragma config FCANIO=OFF
The pins on the PIC32MX795 microcontroller
used by signals for the CAN1 controller to
connect to its transceiver are shared with two
of the signals for UART3A and SPI port 3A.
Jumpers JP1 and JP2 are used to select the
use of these two signals. Place JP1 and JP2 in
the CAN position for use of the CAN1 network
interface. Place JP1 and JP2 in the PMOD
position for use of these signals for UART or
SPI operation. These signals connect to pins 1
& 4 of Pmod connector JF. When JP1 and JP2
are in the CAN position, Pins 1 & 4 of Pmod
connector JF are not useable.
There is no standard connector for use with
CAN networks. The Cerebot 32MX7 board
provides two 2x6 pin header connectors for
access to the CAN signals. Connector J9
provides access to the signals for the CAN1
network controller, and connector J10 provides
access to the signals for CAN2. Refer to the
schematic for the Cerebot 32MX7 board for
information on the connectors and signals.
Digilent 6-pin or 2x6 to dual 6-pin cables can
be used to daisy chain Digilent boards together
in a CAN network. A Digilent 6-Pin cable in
combination with a Digilent PmodCON1 Screw
Terminal Connector module can be used to
connect the Cerebot 32MX7 board to other
network wiring configurations.
The CAN network standard requires that the
network nodes at each end of a network
provide 120 ohm termination. The Cerebot
32MX7 provides the termination resistors and
jumpers to enable/disable the termination
resistors depending on the location of the
board in the network. Jumper JP5 is used to
enable/disable the termination resistor for the
CAN1 network connector, and JP7 is used to
enable/disable the termination resistor for
CAN2. Install a shorting block on the jumper
pins to enable the termination resistor, or
remove the shorting block to disable the
termination resistor.
I
2
C™ Interfaces
The Inter-Integrated Circuit (I
2
C
TM
) Interface
provides a medium speed (100K or 400K bps)
synchronous serial communications bus. The
I
2
C interface provides master and slave
operation using either 7 bit or 10 bit device
addressing. Each device is given a unique
address, and the protocol provides the ability
to address packets to a specific device or to
broadcast packets to all devices on the bus.
Refer to the Microchip PIC32MX7XX Data
Sheet and the PIC32 Family Reference
Manual for detailed information on configuring
and using the I
2
C interface.
The PIC32MX795 microcontroller provides for
up to five independent I
2
C interfaces. The
Cerebot 32MX7 is designed to provide
dedicated access to two of these interfaces
I2C #1 and I2C #2. There are two sets of
connectors on the board for access to the two
I
2
C ports. Connector J8 provides access to
I2C #1 while connector J7 provides access to
I2C #2.
Each I
2
C connector provides two positions for
connecting to the I
2
C signals, power and
ground. By using two-wire or four-wire MTE
cables (available separately from Digilent) a
daisy chain of multiple Cerebot 32MX7 boards
or other I
2
C-capable boards can be created.
The I
2
C bus is an open-collector bus. Devices
on the bus actively drive the signals low. The
high state on the I
2
C signals is achieved by
pull-up resistors when no device is driving the
lines low. One device on the I
2
C bus must
provide the pull-up resistors. On the Cerebot
32MX7, I2C #1 has permanently connected
pull-up resistors. I2C #2 provides selectable
pull-up resistors that can be enabled or
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