MC68HC08AZ32A Datasheet, PDF (339/456 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
MSCAN08 Controller (MSCAN08)
Low Power Modes
20.9.1 MSCAN08 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
20-6). The time when the MSCAN08 enters Sleep mode depends on its
activity:
• if it is transmitting, it continues to transmit until there is no more
message to be transmitted, and then goes into Sleep mode
• if it is receiving, it waits for the end of this message and then goes
into Sleep mode
• if it is neither transmitting or receiving, it will immediately go into
Sleep mode
NOTE:
The application software must avoid setting up a transmission (by
clearing or more TXE flags) and immediately request Sleep mode (by
setting SLPRQ). It then depends on the exact sequence of operations
whether MSCAN08 starts transmitting or goes into Sleep mode directly.
During Sleep mode, the SLPAK flag is set. The application software
should use SLPAK as a handshake indication for the request (SLPRQ)
to go into Sleep mode. When in Sleep mode, the MSCAN08 stops its
internal clocks. However, clocks to allow register accesses still run. If the
MSCAN08 is in buss-off state, it stops counting the 128*11 consecutive
recessive bits due to the stopped clocks. The TxCAN pin stays in
recessive state. If RXF=1, the message can be read and RXF can be
cleared. Copying of RxGB into RxFG doesn’t take place while in Sleep
mode. It is possible to access the transmit buffers and to clear the TXE
flags. No message abort takes place while in Sleep mode.
The MSCAN08 leaves Sleep mode (wake-up) when:
• bus activity occurs or
• the MCU clears the SLPRQ bit or
• the MCU sets the SFTRES bit
MC68HC08AZ32A — Rev 1.0
MOTOROLA
MSCAN08 Controller (MSCAN08)
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Technical Data
339