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Chapter 16 Freescale’s Scalable Controller Area Network (S12MSCANV3)
MC9S12XE-Family Reference Manual Rev. 1.07
Freescale Semiconductor
675
16.4.7.1
Description of Interrupt Operation
The MSCAN supports four interrupt vectors (see
Table 16-37
), any of which can be individually masked
(for details see sections from
Section 16.3.2.6, “MSCAN Receiver Interrupt Enable Register
(CANRIER)
,” to
Section 16.3.2.8, “MSCAN Transmitter Interrupt Enable Register (CANTIER)
”).
NOTE
The dedicated interrupt vector addresses are defined in the
Resets and
Interrupts
chapter.
16.4.7.2
Transmit Interrupt
Atleastoneofthethreetransmitbuffersisempty(notscheduled)andcanbeloadedtoscheduleamessage
for transmission. The TXEx flag of the empty message buffer is set.
16.4.7.3
Receive Interrupt
A message is successfully received and shifted into the foreground buffer (RxFG) of the receiver FIFO.
This interrupt is generated immediately after receiving the EOF symbol. The RXF flag is set. If there are
multiple messages in the receiver FIFO, the RXF flag is set as soon as the next message is shifted to the
foreground buffer.
16.4.7.4
Wake-Up Interrupt
A wake-up interrupt is generated if activity on the CAN bus occurs during MSCAN internal sleep mode.
WUPE (see
Section 16.3.2.1, “MSCAN Control Register 0 (CANCTL0)
”) must be enabled.
16.4.7.5
Error Interrupt
An error interrupt is generated if an overrun of the receiver FIFO, error, warning, or bus-off condition
occurrs.
Section 16.3.2.5, “MSCAN Receiver Flag Register (CANRFLG)
indicates one of the following
conditions:
Overrun
— An overrun condition of the receiver FIFO as described in
Section 16.4.2.3, “Receive
Structures
,” occurred.
CAN Status Change
— The actual value of the transmit and receive error counters control the
CAN bus state of the MSCAN. As soon as the error counters skip into a critical range (Tx/Rx-
warning, Tx/Rx-error, bus-off) the MSCAN flags an error condition. The status change, which
caused the error condition, is indicated by the TSTAT and RSTAT flags (see
Section 16.3.2.5,
Table 16-37. Interrupt Vectors
Interrupt Source
CCR Mask
Local Enable
Wake-Up Interrupt (WUPIF)
Error Interrupts Interrupt (CSCIF, OVRIF)
Receive Interrupt (RXF)
Transmit Interrupts (TXE[2:0])
I bit
I bit
I bit
I bit
CANRIER (WUPIE)
CANRIER (CSCIE, OVRIE)
CANRIER (RXFIE)
CANTIER (TXEIE[2:0])