October 2007

Rev 1

1/28

AN2628

Application note

Programming ST10F27x CAN interrupt drivers

Introduction

This application note describes the CAN interrupt drivers of the ST10F27x and provides

programming examples that can be used to define interrupt schemes and write interrupt

drivers. Two C-CAN modules are implemented on ST10F27x, mapped on XBUS.

Interrupt sources, the way the sources of interrupts are identified and the two methods of

handling interrupts are described: One using the hardware features of the CAN modules

and the other through polling internal sources.

Programming the CAN interrupt drivers through CAN hardware features uses the RXIE and

TXIE bits of each message object. All 32 message objects are accessed through interface

registers. Two sets of register are available for each module, for example CANxIF1 registers

can be used to read from a message object whereas CANxIF2 registers can be used to

write into a message object. Whenever a message is transmitted or received by a message

object, the corresponding interrupt is serviced according to its priority (based on the value of

IntId). This method requires minimum CPU overhead and is the preferred method for most

applications.

CAN polling generates an interrupt whenever a successful transmission or reception occurs.

Polling is high in CPU overhead, as the CPU is interrupted every time a message is

acknowledged on the CAN bus. Therefore, programming the interrupt driver using polling is

only recommended for small networks.

Sample programs are provided for each method as examples.

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