Freescale Semiconductor, Inc.
MSCAN Controller
Low Power Modes
Table 17-2. msCAN12 vs. CPU operating modes
CPU Mode
msCAN Mode
STOP
WAIT
RUN
(1)
CSWAI = 1
SLPAK = X
SFTRES = X
CSWAI = X
POWER_DOWN
SLPAK = X
SFTRES = X
CSWAI = 0
SLPAK = 1
SFTRES = 0
CSWAI = 0
SLPAK = 0
SFTRES = 1
CSWAI = X
SLPAK = 1
SFTRES = 0
CSWAI = X
SLPAK = 0
SFTRES = 1
SLEEP
SOFT_RESET
Normal
CSWAI = 0
SLPAK = 0
SFTRES = 0
CSWAI = X
SLPAK = 0
SFTRES = 0
1. X means don’t care.
17.8.1 msCAN12 SLEEP Mode
The CPU can request the msCAN12 to enter this low-power mode by
asserting the SLPRQ bit in the Module Configuration Register (see
Figure 17-6). The time when the msCAN12 enters Sleep Mode depends
on its activity:
• If there are one or more message buffers scheduled for
transmission (TXEx = 0), the msCAN will continue to transmit until
all transmit message buffers are empty (TXEx = 1, transmitted
successfully or aborted) and then goes into Sleep Mode.
• If it is receiving, it continues to receive and goes into Sleep Mode
as soon as the CAN bus next becomes idle.
• If it is neither transmitting nor receiving, it immediately goes into
Sleep Mode.
NOTE: The application software must avoid setting up a transmission (by
clearing one or more TXE flag(s)) and immediately request Sleep Mode
(by setting SLPRQ). It then depends on the exact sequence of
operations whether the msCAN12 starts transmitting or goes into Sleep
Mode directly.
68HC(9)12D60 — Rev 4.0
MOTOROLA
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MSCAN Controller
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