ST92F124 datasheet(346/429 Pages) STMICROELECTRONICS

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CONTROLLER AREA NETWORK (bxCAN)

CONTROLLER AREA NETWORK (Cont’d)

CAN RECEIVE FIFO REGISTERS (CRFRx)

Read / Write

Reset Value: 0000 0000 (00h)

Note: To clear a bit in this register, software must

write a “1” to the bit.

Bit 7:6 = Reserved. Forced to 0 by hardware.

Bit 5 = RFOM Release FIFO Output Mailbox

- Read/Set

Set by software to release the output mailbox of

the FIFO. The output mailbox can only be released

when at least one message is pending in the FIFO.

Setting this bit when the FIFO is empty has no ef-

fect. If at least two messages are pending in the

FIFO, the software has to release the output mail-

box to access the next message.

Cleared by hardware when the output mailbox has

been released.

Bit 4 = FOVR FIFO Overrun

- Read/Clear

This bit is set by hardware when a new message

has been received and passed the filter while the

FIFO was full.

This bit is cleared by software.

Bit 3 = FULL FIFO Full

- Read/Clear

Set by hardware when three messages are stored

in the FIFO.

This bit is cleared by software.

Bit 2 = Reserved. Forced to 0 by hardware.

Bit 1:0 = FMP[1:0] FIFO Message Pending

- Read

These bits indicate how many messages are

pending in the receive FIFO.

FMP is increased each time the hardware stores a

new message in to the FIFO. FMP is decreased

each time the software releases the output mail-

box by setting the RFOM bit.

CAN INTERRUPT ENABLE REGISTER (CIER)

All bits of this register are set and cleared by soft-

ware.

Read / Write

Reset Value: 0000 0000 (00h)

Bit 7 = WKUIE Wake-Up Interrupt Enable

0: No interrupt when WKUI is set.

1: Interrupt generated when WKUI bit is set.

Bit 6 = FOVIE1 FIFO Overrun Interrupt Enable

0: No interrupt when FOVR is set.

1: Interrupt generation when FOVR is set.

Bit 5 = FFIE1 FIFO Full Interrupt Enable

0: No interrupt when FULL bit is set.

1: Interrupt generated when FULL bit is set.

Bit 4 = FMPIE1 FIFO Message Pending Interrupt

Enable

0: No interrupt on FMP[1:0] bits transition from 00b

to 01b.

1: Interrupt generated on FMP[1:0] bits transition

from 00b to 01b.

Bit 3 = FOVIE0 FIFO Overrun Interrupt Enable

0: No interrupt when FOVR bit is set.

1: Interrupt generated when FOVR bit is set.

Bit 2 = FFIE0 FIFO Full Interrupt Enable

0: No interrupt when FULL bit is set.

1: Interrupt generated when FULL bit is set.

Bit 1 = FMPIE0 FIFO Message Pending Interrupt

Enable

0: No interrupt on FMP[1:0] bits transition from 00b

to 01b.

1: Interrupt generated on FMP[1:0] bits transition

from 00b to 01b.

Bit 0 = TMEIE Transmit Mailbox Empty Interrupt

Enable

0: No interrupt when RQCPx bit is set.

1: Interrupt generated when RQCPx bit is set.

Note: refer to Standard Interrupts Section.

RFOM FOVR

FULL

FMP1

FMP0

WKUIE

FOVIE1

FFIE1

FMPIE1 FOVIE0

FFIE0

FMPIE0

TMEIE

ST92F124 Datasheet(PDF) 346 Page - STMicroelectronics

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