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Chapter 14 Freescale’s Scalable Controller Area Network (S12MSCANV3)
MC9S12XDP512 Data Sheet, Rev. 2.11
Freescale Semiconductor 665
14.4.6.1 Operation in Run Mode
As shown in Table 14-37, only MSCAN sleep mode is available as low power option when the CPU is in
run mode.
14.4.6.2 Operation in Wait Mode
The WAI instruction puts the MCU in a low power consumption stand-by mode. If the CSWAI bit is set,
additional power can be saved in power down mode because the CPU clocks are stopped. After leaving
this power down mode, the MSCAN restarts its internal controllers and enters normal mode again.
While the CPU is in wait mode, the MSCAN can be operated in normal mode and generate interrupts
(registers can be accessed via background debug mode). The MSCAN can also operate in any of the
low-power modes depending on the values of the SLPRQ/SLPAK and CSWAI bits as seen in Table 14-37.
14.4.6.3 Operation in Stop Mode
The STOP instruction puts the MCU in a low power consumption stand-by mode. In stop mode, the
MSCAN is set in power down mode regardless of the value of the SLPRQ/SLPAK and CSWAI bits
Table 14-37.
14.4.6.4 MSCAN Sleep Mode
The CPU can request the MSCAN to enter this low power mode by asserting the SLPRQ bit in the
CANCTL0 register. The time when the MSCAN enters sleep mode depends on a fixed synchronization
delay and its current activity:
Table 14-37. CPU vs. MSCAN Operating Modes
CPU Mode
MSCAN Mode
Normal
Reduced Power Consumption
Sleep Power Down
Disabled
(CANE=0)
RUN
CSWAI = X
1
SLPRQ = 0
SLPAK = 0
1
‘X’ means don’t care.
CSWAI = X
SLPRQ = 1
SLPAK = 1
CSWAI = X
SLPRQ = X
SLPAK = X
WAIT
CSWAI = 0
SLPRQ = 0
SLPAK = 0
CSWAI = 0
SLPRQ = 1
SLPAK = 1
CSWAI = 1
SLPRQ = X
SLPAK = X
CSWAI = X
SLPRQ = X
SLPAK = X
STOP
CSWAI = X
SLPRQ = X
SLPAK = X
CSWAI = X
SLPRQ = X
SLPAK = X