Datasheet

MSCAN
MC9S12DP256 — Revision 1.1
MSCAN
NOTE: The MCU 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 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 wakeup;
copying of RxBG into RxFG, message aborts and message
transmissions. If the MSCAN is still in bus-off state after sleep mode was
left, it continues counting the 128*11 consecutive recessive bits.
Figure 106 Simplified State Transitions
for Entering/Leaving Sleep Mode
MSCAN
Initialization Mode
In Initialization Mode, any ongoing transmission or reception is
immediately aborted and synchronization to the bus is lost potentially
causing CAN protocol violations. To protect the CAN bus system from
fatal consequences of violations, the MSCAN immediately drives the
TxCAN pin into a recessive state.
The user is responsible for ensuring that the MSCAN is not active when
Initialization Mode is entered. The recommended procedure is to bring
Wait
Idle
Tx/Rx
Message
Active
CAN Activity
CAN Activity &
Sleep
SLPRQ
StartUp
for Idle
(CAN Activity & WUPE) |
(CAN Activity & WUPE) |
(SLPAK & SLPRQ)
CAN Activity
CAN Activity
CAN Activity &
CAN Activity
SLPRQ
SLPRQ
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Freescale Semiconductor, Inc.
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