Freescale Semiconductor, Inc.
MSCAN Controller
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 msCAN12 stops its
internal clocks. However, clocks to allow register accesses still run. If the
msCAN12 is in bus-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 RxBG 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 msCAN12 leaves Sleep Mode (wake-up) when
• bus activity occurs or
• the MCU clears the SLPRQ bit or
• the MCU sets SFTRES.
NOTE: The MCU cannot clear the SLPRQ bit before the msCAN12 is in Sleep
Mode (SLPAK = 1).
After wake-up, the msCAN12 waits for 11 consecutive recessive bits to
synchronize to the bus. As a consequence, if the msCAN12 is woken-up
by a CAN frame, this frame is not received. The receive message buffers
(RxFG and RxBG) contain messages if they were received before sleep
mode was entered. All pending actions are executed upon wake-up:
copying of RxBG into RxFG, message aborts and message
transmissions. If the msCAN12 is still in bus-off state after sleep mode
was left, it continues counting the 128*11 consecutive recessive bits.
Advance Information
292
68HC(9)12D60 — Rev 4.0
MOTOROLA
MSCAN Controller
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