Interrupt sources and identification

AN2628

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Interrupt sources and identification

Interrupts generated by the CAN modules can come from different sources: Global interrupt

sources and individual interrupt sources.

1.1

Global interrupt sources

Four interrupt control registers (XIRxSEL, x = 0, 1, 2, 3) are provided in order to generate an

interrupt from different event sources. Each module is linked to its corresponding XPxIC

register (x = 0, 1, 2, 3). Note that an event source can be connected to several XIRxSEL

registers. In particular, each CAN1 and CAN2 event is connected on two interrupt lines:

The new 16-bit register XIRxSEL (x = 0, 1, 2, 3) is divided into two parts:

When different sources submit an interrupt request, the enable bits (Byte High of XIRxSEL

register) define a mask to select the sources to be associated with the unique available

vector. If more than one source is enabled to issue the request, the service routine must

identify the real event to be serviced. This can easily be done by checking the flag bits (Byte

Low of XIRxSEL register). Note that the flag bit provides information about events which are

not currently serviced by the interrupt controller (since masked through the enable bits),

allowing effective software management even when the related interrupt request cannot be

served: A periodic polling of the flag bits may be implemented inside the user application.

Figure 1.

X-Interrupt basic structure

●

CAN1:

XP0INT, XP3INT

●

CAN2:

XP1INT, XP3INT

●

Byte high

(XIRxSEL[15:8])

Interrupt enable bits

●

Byte low

(XIRxSEL[7:0])

Interrupt flag bits

XIRxSEL[7:0] (x = 0, 1, 2, 3)

XIRxSEL[15:8] (x = 0, 1, 2, 3)

XPxIC.IR (x = 0, 1, 2, 3)

70

15

8

IT Source 7

IT Source 6

IT Source 5

IT Source 4

IT Source 3

IT Source 2

IT Source 1

IT Source 0

Enable[7:0]

Flag[7:0]