MC9S12KG128_10 Datasheet, PDF (323/606 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers

Chapter 9 Freescale’s Scalable Controller Area Network (S12MSCANV2)
The MSCAN is able to leave sleep mode (wake up) only when:
• CAN bus activity occurs and WUPE = 1
or
• the CPU clears the SLPRQ bit
NOTE
The CPU cannot clear the SLPRQ bit before sleep mode (SLPRQ = 1 and
SLPAK = 1) is active.
After wake-up, the MSCAN waits for 11 consecutive recessive bits to synchronize to the CAN bus. As a
consequence, if the MSCAN 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 will be executed upon wake-up; copying of RxBG into RxFG, message
aborts and message transmissions. If the MSCAN remains in bus-off state after sleep mode was exited, it
continues counting the 128 occurrences of 11 consecutive recessive bits.
CAN Activity
StartUp
Wait
for Idle
(CAN Activity & WUPE) | SLPRQ
CAN Activity
CAN Activity &
SLPRQ
Idle
CAN Activity &
SLPRQ
Tx/Rx
Message
Active
SLPRQ
Sleep
CAN Activity
(CAN Activity & WUPE) |
CAN Activity
CAN Activity
Figure 9-45. Simplified State Transitions for Entering/Leaving Sleep Mode
MC9S12KG128 Data Sheet, Rev. 1.16
Freescale Semiconductor
323