MC68HC908AT32 Datasheet, PDF (260/378 Pages) Freescale Semiconductor, Inc – Microcontrollers

MSCAN Controller
23.8 Low-Power Modes
The WAIT and STOP instructions put the MCU in low-power stand-by mode.
23.8.1 MSCAN08 Internal Sleep Mode
The CPU can request the MSCAN08 to enter the low-power mode by asserting the SLPRQ bit in the
module configuration register (see Figure 23-6). This causes the MSCAN08 module internal clock to stop
unless the module is active (such as receiving a message). The SLPAK bit indicates whether the
MSCAN08 successfully went into sleep mode. The application software should use this flag as a
handshake indication for the request to go into sleep mode. If not set after the request, the MSCAN08 is
active and has not yet entered sleep mode. No wakeup interrupt will occur in that case.
MCU
OR MSCAN08
MSCAN08 RUNNING
SLPRQ = 0
SLPAK = 0
MCU
MSCAN08 SLEEPING
SLPRQ = 1
SLPAK = 1
SLEEP REQUEST
SLPRQ = 1
SLPAK = 0
MSCAN08
Figure 23-6. Sleep Request/Acknowledge Cycle
When in sleep mode, the MSCAN08 stops its own clocks, leaving the MCU in normal run mode.
The MSCAN08 will leave sleep mode (wakeup) when bus activity occurs or when the MCU clears the
SLPRQ bit.
The TxCAN pin will stay in a recessive state while the MSCAN08 is in internal sleep mode.
NOTE
The MCU cannot clear the SLPRQ bit before the MSCAN08 is in sleep
mode (SLPAK = 1).
MC68HC908AT32 Data Sheet, Rev. 3.1
260
Freescale Semiconductor