MC912DG128A Motorola, MC912DG128A Datasheet - Page 283

• Manufacturer Part Number: MC912DG128A
• Description: Microcontrollers
• Manufacturer: Motorola

15-mscan12
MOTOROLA
NOTE:
The application software must avoid setting up a transmission (by
clearing one or more TXE flag(s)) and immediately request SLEEP
mode (by setting SLPRQ). It will then depend on the exact sequence of
operations whether the msCAN12 will start transmitting or go 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 msCAN12 stops its
internal clocks. Clocks to allow register accesses will still run. The
TxCAN pin will stay in recessive state. If RXF=1, the message can be
read and RXF can be cleared. However, if the msCAN12 is in bus-off
state, it stops counting 128*11 consecutive recessive bits due to the
stopped clocks. Likewise, copying of RxBG into RxFG will not take place
while in sleep mode. It is possible to access the transmit buffers and to
clear the TXE flags. No message abort will take place while in sleep
mode.
The msCAN12 will leave SLEEP mode (wake-up) when
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 will not be received. The receive message
buffers (RxBG and RxFG) will contain messages if they were received
before sleep mode was entered. Pending copying of RxBG and RxFG,
•
•
•
•
•
•
if it is transmitting, it will continue to transmit until there is no more
message to be transmitted, and then go into SLEEP mode
if it receiving, it will wait for the end of this message and then go
into SLEEP mode
if it is neither transmitting nor receiving, it will immediately go into
SLEEP mode
bus activity occurs or
the MCU clears the SLPRQ bit or
the MCU sets SFTRES.
MSCAN Controller
MC68HC912DT128A Rev 2.0
MSCAN Controller
Low Power Modes
283