ST10F280_12 datasheet(161/239 Pages) STMICROELECTRONICS

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ST10F280

CAN modules

Doc ID 8673 Rev. 3

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As for all other interrupts, the interrupt request flag XP0IR/XP1IR in register XP0IC/XP1IC is

cleared automatically by hardware when this interrupt is serviced (either by standard

interrupt or PEC service).

Note:

As a rule, CAN interrupt requests can be serviced by a PEC channel. However, because

PEC channels only can execute single predefined data transfers (there are no conditional

PEC transfers), PEC service can only be used, if the respective request is known to be

generated by one specific source, and that no other interrupt request will be generated in

between. In practice this seems to be a rare case.

Since an interrupt request of the CAN Module can be generated due to different conditions,

the appropriate CAN interrupt status register must be read in the service routine to

determine the cause of the interrupt request. The Interrupt Identifier INTID (a number) in the

Interrupt Register indicates the cause of an interrupt. When no interrupt is pending, the

identifier will have the value 00h. If the value in INTID is not 00h, then there is an interrupt

pending. If bit IE in the Control Register is set, also the interrupt line to the CPU is activated.

The interrupt line remains active until either INTID gets 00h (after the interrupt requester has

been serviced) or until IE is reset (if interrupts are disabled).

The interrupt with the lowest number has the highest priority. If a higher priority interrupt

(lower number) occurs before the current interrupt is processed, INTID is updated and the

new interrupt overrides the last one. The Table 31 lists the valid values for INTID and their

corresponding interrupt sources.

Interrupt Register

Address:

0xEF02h / 0xEE02h XReg

Reset:

0x--XXh

Type:

Reserved

INTID

INTID Interrupt Identifier

This number indicates the cause of the interrupt. When no interrupt is pending, the value will

be “00”.

Table 31.

INTID values and corresponding interrupt sources

INTID

Cause of the Interrupt

Interrupt Idle: There is no interrupt request pending.

Status Change Interrupt: The CAN controller has updated (not necessarily changed) the

status in the Control Register. This can refer to a change of the error status of the CAN

controller (EIE is set and BOFF or EWRN change) or to a CAN transfer incident (SIE must

be set), like reception or transmission of a message (RXOK or TXOK is set) or the

occurrence of a CAN bus error (LEC is updated). The CPU may clear RXOK, TXOK, and

LEC, however, writing to the status partition of the Control Register can never generate or

reset an interrupt. To update the INTID value the status partition of the Control Register

must be read.

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