AN2341

Handling interrupts

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Note:

This example assumes that a ‘switch on IntId’ instruction is placed at the beginning of the

interrupt driver:

case (intid):

// Message n specific interrupt

CANxIF1CM = 0x7F;

// Transfer entire message into inference

CANxIF1CR = intid;

// register and clear IntPnd and NewDat

CANx_WAIT_FOR_IF1;

if (CANxIF1A2 & IF_DIR)

// direction = transmit

{

if (CANxIF1MC & IF_NEWDAT) // remote received provided that

// UMask =1 and RmtEn = 0

{.....} // procedure to handle answer to remote

else

{.....} // procedure to handle transmit interrupts

}

else

// direction = receive

{

if (CANxIF1MC & IF_NEWDAT) // NewDat is set

{.....} // procedure to handle data receive interrupt

else

{.....} // a remote frame was successfully transmitted

}

break;

2.2

Bus-off interrupts

Each transfer error detected on the CAN bus (though not necessarily generated by the CAN

module) increments one of the two error counters (receive error counter and transmit error

counter). If one of these counters reaches the value of 96, bit EWarn is set. If enabled by

bits EIE and IE, an error interrupt is generated. If the transmit error counter exceeds the

value of 255, bit BOff is set. If enabled by bits EIE and IE, this generates an error interrupt.

Furthermore, when the device goes into the bus-off state, bit INIT is set and all actions on

the bus are stopped immediately.

The bus-off recovery sequence can be initiated from the bus-off state. During the bus

recovery sequence, the CAN module monitors the recovery sequence.

●

The bus-off recovery sequence is started by resetting bit INIT.

●

Bit0Error is set every time a sequence of 11 recessive bits is detected. Bit0Error

indicates that the CAN bus is not stuck at dominant or not continuously disturbed. If bits

SIE and IE are set, a status interrupt is generated after each sequence.

●

The recovery sequence cannot be shortened by setting or resetting bit INIT.