XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 274

• Manufacturer Part Number: XC912BC32CFU8
• Description: M68HC12B Family Data Sheet
• Manufacturer: Motorola Semiconductor Products

msCAN12 Controller
Data Sheet
274
NOTE:
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 then
depends on the exact sequence of operations whether the msCAN12 starts
transmitting or goes 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. However, clocks to
allow register accesses still run. If the msCAN12 is in bus-off state, it stops counting
the 128 x 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 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 (wakeup) when one of these occurs:
The MCU cannot clear the SLPRQ bit before the msCAN12 is in sleep mode
(SLPAK = 1).
•
•
•
Bus activity occurs.
MCU clears the SLPRQ bit.
MCU sets SFTRES.
OR MSCAN12
MCU
MSCAN12 SLEEPING
Figure 16-6. Sleep Request/Acknowledge Cycle
SLPRQ = 1
SLPAK = 1
msCAN12 Controller
MSCAN12 RUNNING
msCAN12
SLPRQ = 0
SLPAK = 0
SLEEP REQUEST
M68HC12B Family — Rev. 8.0
SLPRQ = 1
SLPAK = 0
MCU
MOTOROLA