Freescale Semiconductor MPC5200B - Manual (Page 675)

MPC5200B Users Guide, Rev. 1
19-36 Freescale Semiconductor
Functional Description
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 wake-up; 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 19-10. Simplified State Transitions for Entering/Leaving Sleep Mode
19.7.8.5 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.
NOTE
The user is responsible for ensuring that the MSCAN is not active when Initialization Mode is
entered. The recommended procedure is to bring the MSCAN into Sleep Mode (SLPRQ=1 and
SLPAK=1) before setting the INITRQ bit in the CANCTL0 register. Otherwise the abort of an
ongoing message can cause an error condition and can have an impact on the other bus devices.
In Initialization Mode, the MSCAN is stopped. However, interface registers can still be accessed. This mode is used to reset the CANTCTL0,
CANRFLG, CANRIER, CANTFLG, CANTIER, CANTARQ, CANTAAK, CANTBSEL registers to their default values. In addition it enables
the configuration of the CANBTR0, CANBTR1 bit timing registers, CANIDAC and the CANIDAR, CANIDMR message filters.
Section
19.5.3, MSCAN Control Register 0 (CANCTL0)—MBAR + 0x0900 / 0x980 for a detailed description of the Initialization Mode.
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