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3.7. CAN interface

The IM-AD1 has two CAN interfaces provided by Bosch CC770 serial communications controllers. The network interfaces are provided by Philips TJA1050 transceivers, each capable of 1Mb/s data transfer.

Figure 3.8 shows the architecture of the CAN interface. The CAN controllers are 5V devices and are supported by buffers at their interface with the 3.3V system buses provided by the logic module. The CAN controllers are configured to operate with an 8-bit non-multiplexed asynchronous host interface. Each of the CAN controllers has a 16MHz crystal that it uses for its internal clocks.

Figure 3.8. CAN interface architecture

CAN interface architecture

All interface signals are routed to the logic module. The CAN controllers are supported by an AHB interface instantiated into the logic module code example supplied with the IM-AD1.

The transmit and receive data signals, CANx_TXD and CANx_RXD, at the EXPIM connectors are not used for the normal operation of the interfaces. They are provided to allow you to implement your own CAN controller logic in the logic module FPGA.

The surface mount links, LK1 and LK2, are provided so that the transmit data signals to the TJA1050 transceivers can be driven either from the CAN controllers or directly from the logic module FPGA.

Table 3.8 shows the assignment of the CAN controller interface signals to the logic module signals on the EXPIM connector.

CAN interface signal assignment
SignalEXPIM connectorDescription
CAN_A[7:0]IM_BBANK[7:0]CAN address bus
CAN_D[7:0]IM_BBANK[8:15]CAN data bus
CAN_T/RIM_BBANK16CAN buffer direction control
CAN_nOEIM_BBANK17CAN buffer output enable
CAN1_nRESETIM_BBANK18CAN1 reset signal
CAN2_nRESETIM_BBANK19CAN2 reset signal
CAN_R/nWIM_BBANK20CAN read / write
CAN1_nCSIM_BBANK21CAN1 chip select
CAN2_nCSIM_BBANK22CAN2 chip select
CAN1_TXDIM_BBANK23CAN1 transmit data
CAN2_TXDIM_BBANK24CAN2 transmit data
CAN1_nDSACK0IM_BBANK25CAN1 data acknowledge
CAN2_nDSACK0IM_BBANK26CAN2 data acknowledge
CAN1_nINTIM_BBANK27CAN1 interrupt
CAN2_nINTIM_BBANK28CAN2 interrupt
CAN1_RXDIM_BBANK29CAN1 receive data
CAN2_RXDIM_BBANK30CAN2 receive data

You connect the CAN interfaces through the 9-pin D-type plugs J3A (top) and J3B (bottom), with CAN1 connecting to J3A.

Figure 3.9 shows the pin locations for this type of connector.

Figure 3.9. CAN connector pin locations

CAN connector pin locations

Table 3.9 shows the signal assignment.

CAN connector signal assignments
PinJ3AJ3B
1Not connectedNot connected
2CAN1_LCAN2_L
3GNDGND
4Not connectedNot connected
5GNDGND
6GNDGND
7CAN1_HCAN2_H
8Not connectedNot connected
9Not connectedNot connected
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