Freescale’s Scalable Controller Area Network (S12MSCANV3)
8.4.5.7
Disabled Mode
The MSCAN is in disabled mode out of reset (CANE=0). All module clocks are stopped for power saving,
however the register map can still be accessed as specified.
8.4.5.8
Programmable Wake-Up Function
The MSCAN can be programmed to wake up from sleep or power down mode as soon as CAN bus activity
is detected (see control bit WUPE in MSCAN Control Register 0 (CANCTL0). The sensitivity to existing
CAN bus action can be modified by applying a low-pass filter function to the RXCAN input line (see
control bit WUPM in Section 8.3.2.2, “MSCAN Control Register 1 (CANCTL1)”).
This feature can be used to protect the MSCAN from wake-up due to short glitches on the CAN bus lines.
Such glitches can result from—for example—electromagnetic interference within noisy environments.
8.4.6
Reset Initialization
The reset state of each individual bit is listed in Section 8.3.2, “Register Descriptions,” which details all
the registers and their bit-fields.
8.4.7
Interrupts
This section describes all interrupts originated by the MSCAN. It documents the enable bits and generated
flags. Each interrupt is listed and described separately.
8.4.7.1
Description of Interrupt Operation
The MSCAN supports four interrupt vectors (see Table 8-39), any of which can be individually masked
(for details see Section 8.3.2.6, “MSCAN Receiver Interrupt Enable Register (CANRIER)” to
Section 8.3.2.8, “MSCAN Transmitter Interrupt Enable Register (CANTIER)”).
NOTE
The dedicated interrupt vector addresses are defined in the Resets and
Interrupts chapter.
Table 8-39. Interrupt Vectors
Interrupt Source
CCR Mask
Local Enable
CANRIER (WUPIE)
Wake-Up Interrupt (WUPIF)
Error Interrupts Interrupt (CSCIF, OVRIF)
Receive Interrupt (RXF)
I bit
I bit
I bit
I bit
CANRIER (CSCIE, OVRIE)
CANRIER (RXFIE)
Transmit Interrupts (TXE[2:0])
CANTIER (TXEIE[2:0])
8.4.7.2
Transmit Interrupt
At least one of the three transmit buffers is empty (not scheduled) and can be loaded to schedule a message
for transmission. The TXEx flag of the empty message buffer is set.
S12P-Family Reference Manual, Rev. 1.13
Freescale Semiconductor
301
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